P E R M AN ENT FO RTI FICATION

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STAVE F E BE E R GU . I G J ,

r f r f r i ri P o esso o C ivil and M ilita y E ng nee ng.

WE ST P O IN T

P R E SS or U s m urmur A cunnn r

C O N T E N T S .

P A G E

C HA PT E R I .

LAND DEFEN SES A N D THEIR DEV ELO P M E N T . — — m —I d a . n B a e o t s. t e e s C lasses of lan d defen se . rri r f r In r nch c p —E e t of m eans of att a k— o de a t ner line of defense . ff c c M rn r il

T R C H A P E II .

P R O FI LE A N D TR ACE . — —R m — r fi . P . P N o menclat fi re of t he p o le arade a part arapet . — — — t . ar . o r D t . C et e Se C u te s a . C o e d T erre plein . i ch un p n c rp v re — — — — T . B ast o t a e . P o o na a G a s . ac e t e . way . l ci r i n r c lyg l r c — — t o A dva ed w o s . e wo s O ut works . nc rk In ri r rk

A P T E R C H III .

A N A C N ST R UC T E D B T N 1 -1 L ND DEFE SE S C E W EE 870 880. — l . . . nter o E x D T ype of wo rks . T race I i r ine ample etached — — — nne lineI R é su é . B a e o t s fo rt s . I r m rri r f r

C A P T E R H IV .

A D D N IN 1 L N EFE SES S CE 880. — — — . F t F o t F o t w t ee o W t out ee . o t A rm ored f r r i h k p r i h k p r ins. — un . e d fo r 21 o r 1 . . a e H T urret f t wo 6 c m c lib r g S Shi l c . m . ow

t . T an o t a rr A o d n s s e t t . it z er . rm re fro r p r bl u e s Mo rt ar — — d W o s fo r nea and d st a t de e se . B a e shiel rk r i n f n rri r F ort s . — R a wa s A ccesso ry defense . il y

A P E R C H T V . P R INCIP LES O F LAND D EFEN SE ILLUST R ATED B % T HE FO R TIFICATIO NS F R A O N T HE G R M A R TI R O F NCE E N F O N E . — — — — A B a . . m u d T o o a f se s . o Scheme o defen r ie n ry p gr phy . L ines — 1 d o e a n — o f t a o t . o t a an e t F r nsp r P li ic c mm rci l c res. rench — — o fi a n t h G e a o t e . B o a L f rti c ti o ns o e rm n fr n i r und ry . ines of — l — t d —P F o tie e . e e at e e . a defense . r n r in In rm i lin ris

P T E R C HA VI .

SE A - O A T D A N D AV A ATTA C S EFENSE N L CK . — — — B t . A r d N aval vessels. at leships m ore cruisers C o ast defense — — vesse s . U a o ed ves e s . et ods of at t l n rm r s l M h ac k . C O T T N E N S .

P A G E

C H A P T E R VII .

M T O F O A T D ELE EN S C S EFE N SE . — . . in l G unS o t a s T o edoes . u m a nl e a )o M r r rp S b rine S . H r r de f s — b t r i I — s O s uc t O I S . T do oat s en e ves el s . orpe b 54

A P E R C H T VIII .

T U R R T A E M A T A N D B A R R TT ATT R I . E S , C S ES , E E B E ES — — — — a m . . B a D a a T urret s . C se at es Shields arbett e b t teries is ppe r

A P T R C H E IX .

A R R AN M N T O F O A T D K G E E C S EFE N S E W O R S .

— — — c N f n . L f C aliber O f gunS . umber O gu S ine O f defense E ffe t o — - fi r — R n n r a . fi s elev t i on High angle e a ge and po sit i on de . — — I ) f n a ain t nd t o s . F o nt . s st ire c rol e e se g l a parties . O b ruc i n E xam e a and O f n f am t on pl , hydrogr phy line defe se O H p

R o ads , Va L I S T O F P L A T E S .

P L A T E — nd 4. 1 P fi f e t o . 2 a o . F a w I igures . ro le O perm n n rk , 3 P lyg

B va m t . on al t race . 5. astio n t race . 6 . Mo ble e placemen s A me t O f t a t t i . 7 . rrange n r di o r ba ter es

T t t fi a II . ype of b as ion system O f for i c ti on .

T f O f III . ype O p o lygon al syst em defense .

D t d f E . IV . e ache fo rt or int renched camp ( nglish type)

. D e f V efen s s o St rasburg.

F m on . o t w B ri l VI r it h k eep ( a t ).

. F r VII ort wit h out keep ( B ialm ont ).

T r . a f B ri m nt VIII i ngul ar trace used in defenses O Meuse ( al o ).

o r o IX . G rus n turret fo t w 15 cm . guns .

. S d f r 1 it z . u t t . X hiel o 2 cm . h ow er G r son disappearing urre

— ’ F i 1 . F t XI . gures irs li ne Schum an s system O f fort ificat ion . ’ ’

2. d m a e o n e s t . T d S c lin Schu n sys em 3 . hir line Schum an s ’

4 . fi f P o e O te . system . r l Schum an s sys m

f 1 G so s e o r . t XII . ru n hi ld 2 cm m ortar. G ruso n ransportable. t u r r et .

e - e a d XIII . S mi p rm nent infant ry re out for intrenched camp E ( nglish type ).

- h XIV . Siege gun b attery ( E nglis type).

. F a d d n n t XV rench l n efe ses o he G erman front ier .

X I B V . at tleship O regon .

F — . 1 . A 2 s . t XVII igure rm o red cruiser N ew %o rk . C oas defense v essel Mont erey . — . F u es 1 . B o a t e . 2 . C t for ud XVIII ig r u y n min ircui j gment mine . 3 . C t for a d A ra fo ircui regul te mine . 4 . r ngement r a grand f group O mines . — . F es 1 and 2 . G uso a ate an 4 XIX igur r n c sem . 3 d . Section and plan for an emplacement for a b arbette gun on a disap

pearing carriage .

’ ’ . C o ast de e ses a t on r m XX f n , H mp R oadS , Vi gm .

CHAPTER I .

A N D DE F E N S S A N D T E R DE E L L E H I V O PME N T .

Permanent land defenses are the fortifications which are constructed on the land frontiers , or in the interior of a country , during time O f peace , in anticipation O f invasion m at some future time by a hostile ar y . Their O bject is to assist the land forces of a nation to defend it against such invasion , by rendering selected strategical points secure against the operations of the hostile army . Land defenses therefore bear the same relation to

‘ strategy as hasty intrenchments do to battle field tactics ; the O bject of each is to increase the resisting power of a body of troops detailed to hold a point which is important both to the defense and to the attack . — C lasses of L and Defenses. The permanent land de fenses which are being constructed , or are O f military value barri r ort i tr to d ay , may be divided into e f s and n enched camp s. ’ F — r r r B arrier orts . A barrier fo t , or fo t d a rét, is any fortification which is intended to arrest the advance of a m hostile army at so e point on a natural line of O perations . m They are usually constructed in a ountainous country , where railways and highways are widely separated and are confined to narrow valleys or canons , which render it impossible to construct branch lines around the forts . The following historical examples explain the functions oi ' these fortifications

In the spring of 1800, while one part O f the Austrian army in Italy was besieging General Massena in Genoa , u Su u and another was purs ing General chet thro gh Nice , N apoleon was secretly organizing in Switzerland the Army D LAN DE FE NSE S .

O f the Reserve of m en with which he proposed to relieve both his generals . His plan was to cross the A l ps B at the Great St . ernard pass , move rapidly down the val ley O f Aosta , and place himself along the Ticino between the Austrian army and its base , thus compelling the latter to retreat and to fight for its communications . On the 15th

of May , his army began to cross the mountains , and four days later the advance guard was stopped by Fort B ard on the Doria river , which prevented the passage of its artillery o f and wagons . This fort c nsisted O a citadel on a high ,

isolated rock close to the river , and only one hundred and - twenty five yards from the highway through the valley .

The citadel was surrounded by two exterior walls , had a

garrison O f 400m en , and an armament O f 18 gun s : For a time it seemed as though this little fort would defeat the plans O f Napoleon and render useless the passage O f the

A l ps . Six days were spent in constructing trails over the O f mountains for the passage the cavalry and infantry , during which time every available effort was made to com

pel the small garrison to surrender . As these efforts were

fruitless , and as the other arms needed the support O f

artillery , it became necessary to force the passage . The m guns were therefore oved by at night , precautions being taken to reduce the noise by wrapping the wheels with m m straw , and to conceal the ove ent by making a cloud O f

smoke . In spite O f these precautions many O f the pieces

were dismounted by the fire of the fort . E ven when the

army had passed , the fort was still a dangerous O bstacle

on the line of retreat in case O f defeat , therefore Napoleon was compelled to detach a division to take it by regular

Siege . Had F B m ort ard not stopped the advance of the ar y ,

it is probable that Genoa never would have fallen , as the Austrian army besieging that place received orders to

raise the siege and join the main body on the very day ,

June 2nd, that Massena had exhausted his supplies and

was compelled to surrender . I F R 'r B ARR E R O s. 3

n - m In the Fra co Ger an war the fortress of Toul , [P] . - XV] controlled the Paris Strasburg railway . It was an m m old work with a weak garrison , a defective ar a ent , and was commanded on all Sides by heights only a mile away . The Third German army appeared before it on the 14th of August and after a futile bombardment left an investing force and marched on . % Although the fortress placed no important O bstacle f m in the way O the advance of the Third ar y , still the transport of supplies and stores of every description was mu in O f um - ch delayed , spite the use of n erous by roads , and ran some risk from the attacks O f marauding gardes - mobiles and franc tireurs . The conveyance O f sick and ‘ wounded to the rear became continually more difiicul t as the army advanced , and the time was indefinitely post poned when it would be possible for the transport depart ment to bring to the front , as rapidly as was desired , the artillery stores O f all descriptions required for the contem r plated siege O f Paris . O u complete and excellent railway organization became paralyzed at Toul , so that even at this time the advisability of constructing a line branching off from Frouard was being considered . Thus from the m f undeniable present strategical i portance O the fortress , ” the occupation of Toul had become for us a necessity . Tiedemann Siege Operations in the C ampaign against ” France .

Toul fell on the 23rd of September , about one week after the complete investment of Paris . Had it been a - first class barrier fort , well supplied with provisions and ammunition , the Germans would have been obliged to con struct the branch line mentioned , notwithstanding the nu f favorable topographical features O the country . A simple barrier fort is usually planned for passive defense only , the garrison , armament , and supplies are thoroughly protected from bombardment and advantage is taken O f the topographical features of the site to render an ffi assault impracticable , and a siege very di cult . — I ntrenched C ar ma A n intrenched camp as its. mam a 4 LAND DE FE NSES . implies is a fortress of very great magnitude which m ay m u beco e the ref ge of a defeated and demoralized army . nl It can o y be invested by a large force , and is defended m by active as well as by passive easures . In one sense it is a battle field organized for defense by occupying the sup m porting points with per anent fortifications . The line O fde m m O f fense for s the peri eter a polygon , and incloses either m r l u O f f a ilita y nuc e s consisting arsenals , depots O supply , nu f etc . , or a civil cleus consisting O some important polit mm ical or co ercial centre . If no civil centre is inclosed , the camp is called a military camp . The theoretical dis tance O f the line of defence from the nucleus is usually - m about four and one half iles , which is based upon the m m di O f extre e bo bar ng range heavy siege artillery , and the distance at which these batteriescan be established in n O f the O f fro t line defense without first capturing that line . m m di The extre e bo bar ng range is about six miles , and the least distance O f the bombarding batteries from the line m - of defense is assu ed to be one and one half miles . In O f actually locating the line defense upon the ground , this theoretical distance is varied to conform to the topograph

ical features O f the site , and the strategical or tactical mu ul u . f nctions which it st f fil In the defenses of Strasburg ,

for topographical reasons , the line of defense constructed between 1870 and 1880 is from to 5 miles from the

nucleus , and in the defenses O f Paris , constructed about m m the same ti e , for ilitary and political reasons , the line m of defense is iles from the nucleus . The line of de

feuse is a line with intervals; that is , it consists either O f f single redouts or forts , or groups O works , upon the sup

porting points , separated by intervals , which vary from

one to three miles . The interval between the individ f ual works , or groups O works , is dependent upon their

separate strength ; because the weaker the work , the more f necessary will be the support O the adjacent ones . The theoretical intervals are greatly modified by the topography of the site and by the military functions O f each work or n ur r u . g o p In the defe ses of Strasb g, for topographical I I NNE R L NE . 5

reasons , the intervals on the west bank vary from of a m mile to iles . In the defenses O f Paris , for topograph ical and financial reasons , there are two undefended inter vals O f miles between adjacent groups of works in the exterior line . i — I nner L ne of Defense. I f a line with intervals were the only barrier guarding a large city , and the garrison m were co paratively weak , it would be possible for an energetic assail ant to penetrate the intervals with a raiding f party under cover O darkness or fog , and capture or de u stroy the city witho t attacking the forts . T O defeat such a movement it is customary to surround the city with an enceinte or continuous line O f fortifications ; that is , a line without a break in the continuity of rampart , parapet and ditch . A fortification which will defeat the efforts of a raiding party with field-gun s is considered sufiiciently strong for the inner line . B arrier forts and intrenched camps are employed either m m - singly , or in co bination , to for bridge heads , pivots of maneuvre , fortified curtains , and fortified regions . B ridge heads are constructed around the bridges over wide deep rivers in such a manner as to secure the bridges from attack , and to allow the defending armies to O perate with safety on either bank . P ivots of maneuvre are large forti fications which serve as pivoting points for the operations i of an army in the field . F ort fied curtains are lines of fortification , constructed near an O pen frontier to bar the advance O f an invader ; they usually consist of intrenched

‘ camps connected by a line O f barrier forts . F ortified regions are tracts O f country surrounded by a number O f in ’ trenched camps ; the camps are distant two or three days march from one another . The region serves as a refuge to a large army in retreat , in which it cannot be invested .

The great fortresses of the Rhine , C ologne , M ayence , - and Strasburg [P L XV] are bridge heads , which will cover the advance and retreat O f the German armies across that river . Metz [P l . XV] is a pivot of maneuvre which will support one flank of a German army op eratin g Rd Sm . 6 LAND DE FE NSE S .

f L r province O or aine . The eastern frontier O f F rance ( Pl . XV) has two defensive curtains Verdun to Toul and E pinal to B elfort , which will be described hereafter . The cele brated quadrilateral of Italy comprising the fortresses of L Verona , egnano, Peschiera , and Mantua is an intrenched region ; intrenched regions also form part of the new de n fe ses of France and Russia . — E fi ect of M eans of A ttach The art of permanent fortification is dependent upon the weapons and m achine s especially designed for the attack and defense of per manentl y fortified positions . Before the invention of gun powder , a high inclosure wall with a pathway or boulevard on top , protected by a crenelated parapet wall , and also m provided with a achicoulis gallery or flanking towers , was sufficient to ward off an attack by an enemy , whose weapons were spears , bows , and slings , and whose machines W were scaling ladders . hen the besieger invented the battering ram , the defender strengthened his wall by con structing counterforts and backing his wall by a heavy mound O f earth . Attack by mining was met by the con

~ struction of a wide , deep ditch in front of the wall . The invention of gunpowder led the besieger to replace the battering ram by guns which could destroy the walls across the ditch . The defender met this attack by masking his wall by a glacis , and by constructing additional works be yond the ditch , which prevented the besieger from estab lishing his batteries upon the glacis until he had captured these advanced works . The wall was still considered the main line of defense , and to prevent the enemy reaching it , the ditch was thoroughly swept by fire of artillery and sm all arms . As the besieger improved his artillery , the defender was obliged to move his advanced works still further to the front . In some fortifications these works were built in front of the glacis , but in close range of it , and in others m m they were practically detached fro the ain line of defense , and beyond supporting distance from it . When rifled ar m tillery was introduced about the iddle of this century , the general character of the permanent land fortifications E FF E C T O F A RT ILLE R%. 7

P in existence was as described above [ l . II] . A contin uous wall , 30to 36 feet high , with a continuous parapet for the artillery and infantry in its rear , extended around the r city . In advance of this wall was a d y or wet ditch , 60or more yards wide , and beyond the ditch were a number of additional works also surrounded by ditches , which could be swept by the close fire of the works in rear , or from the main work . Surrounding all the works was a glacis which masked all walls from the fire of the enemy . A few forti

fications had works beyond the glacis . T he defenses were - as a rule O pen defenses with few bomb proofs , and were especially designed to protect the defenders against ricochet

fire, the most dangerous fire which could be brought against them . The Franco-German war was the first in which rifled siege artillery was used against the permanent works . In 1864 the Prussians introduced into their armament the 15 - 1 1 c . m . inch ) rifled siege gun , and in 870 the 5 c . m . siege howitzer , and the 21 c . m . inch ) rifled siege mor tar . With this artillery the Germans were able to destroy - existing bomb proofs , breach scarp walls masked by a glacis as then constructed , render open shelters untenable , and bombard cities at a range of about five miles . Out of twenty-five castles and fortified cities taken by the Ger mans , four made no defense whatever, and sixteen yielded after one or more bombardments ; many O f them being - bombarded by rifled field guns only . Modern fortification m may then be said to date from this war , since which ti e several million dollars have been spent by each of these two countries alone , in modifying the permanent fortifi cations O n their common frontier . r — M odern A rtille y . While few pieces of greater calibre than those used by the Germans in this war have since been introduced into the heavy siege or fortress artillery m of any country , any changes have been made to render the pieces more effective . B y the use of better steel , longer guns , and smokeless powders , the range and accuracy of the - un i zer m rtar have been w em siege g , how t , and o g LAND DE FE NSES . creased ; and by the use of Shrapnel and torpedo Shells in curved and vertical fire , the howitz er and mortar have almost supplanted the gun in attack and defense . T h e introduction of machine and rapid fire guns has greatly aided the defense in reducing the Size of the garrisons for passive defense , and the extent of shelter required for the same amount of fire delivered . The latest types of heavy siege and fortress artillery have all been introduced since 1 12 1880. The standard calibres are the 5 c . m . and c . m . 2 1 guns , and the 1 c . m . and 5 c . m . howitzers and mortars . m The extreme ranges , of the guns are fro to yards , of the howitzers to yards , of the mortars to The guns are employed with Shrapnel against live targets at all ranges and against captive balloons ; with m torpedo shells , against live targets , to breach asonry , to destroy villages , camps , and parks , and to destroy guns which project from armored turrets and Shields . T he howitzers and mortars are employed with shrapnel and torpedo Shells to reach live targets protected by open or l covered shelters , and with torpedo she ls to destroy earth - works and all varieties of bomb proofs and magazines . CHAPTER I I .

P R O F IL E A N D T R A C E .

— N omenclature of the P rofi le P l . I , Fig . I , is the pro file of a permanent fortification in which

A B is the plane of site .

T U, the surface of the ground in the interior of the m n work , is the p arade. The ound of earth which is co structed on the plane of site and which is limited by the r m r planes OP and A B , is the a p a t. m m r R S , the wall which ter inates the ra part in rea , is the p arade wall . m OP and QR , the horizontal surfaces of the ra part are - r the terre p leins; OP the upp er, and QR the lowe . a P Q is the ramp rt slop e. A similar slope connects the - lower terre plein and the parade in some works .

MNO is the parap et, the planes and lines of which have

the same designations as in field fortification . m L is t he ber .

F G HI KL is the ditch.

LK is the earthen scarp .

K is the exterior corridor.

I J is the detached scarp wall .

H is the cunette.

F G is the counterscarp wall .

F E is the covered way .

C DE is the glacis.

The thickness , height , command , and relief of the

parapet are measured as in field fortification . The prin

cipal line of works with masonry scarp walls , is the mag

istral , or line of intersection of the face and top of the m m ur m scarp wall . It is the line fro which all eas e ents 9 I O LAND DE FE NSES .

ma r fir li m u th are de in the t ace , and the st ne arked pon e ground in laying out the work . — P arade. I n large works the parade coincides with the site upon which the fortification is built ; in small ones it may be above or below the site . — R amp art I n early fortifications the rampart was made high enough to give the interior crest of the parapet a command of from 20to 30 feet over the plane of site and this height is retained in some modern works . On account of the extreme accuracy of modern artillery , the very recent works have little command over the ground in their immediate vicinity , so that they m ay be better concealed m ’ fro the assailant s batteries . Underneath the rampart - are the bomb proofs for magazines , quarters , etc . — P arap et To resist the continued fire of heavy siege guns , the parapet is made from 23 to 26 feet thick , the in angles the profile are rounded , and the exterior slope is given as little inclination as practicable . In the most recent works the triangular profile is employed as it is less easily destroyed by torpedo shells of howitzers and mor tars ; the parapet is made about 40feet thick . - — T erre P lein . I n early fortifications there was but a - single terre plein , from 14 to 16 yards wide , which served as a barbette for artillery , and formed a wide roadway around the work in rear of the guns . As curved fire became more accurate , the roadway . was made at a lower m - level and for ed a second terre plein . In the most recent works , the artillery is either protected by armor , or is placed in separate batteries , and the communications are protected by overhead cover ; the terre-plein has therefore ceased to be of any special value and is simply a limiting surface of the rampart . — Ditch A ditch 30 to 60 yards wide and 18 to 20 feet deep , with masonry scarp and counterscarp , was one of the principal features of all permanent fortifications until 1886 ; since that time there has been a tendency to adopt the m u triangular profile with a shallow ditch , and rely ore pon

LAND DE FE NSES .

— C overed Wan I n early works , a covered way ten or more yards wide , was a very important feature O f a forti

fication, as it was the base from which all sorties were made against the assailant . At the present time sorties are not made from the work itself , and as a wide covered way exposes the scarp slope and barrier to curved fire which grazes the crest of the glacis , it is wholly omitted or its width is decreased to one yard and serves as an outpost line for sentries . — G lacis . The glacis is constructed to remove all dead angles in front of , and near , the fortifi cation . With low commands the glacis almost disappears . — T race. T he trace of a fortification is usually designed by laying out on the plane of site , a broken line, separating the positions or objects which are to be held , from the positions which may be occupied by an assailant . E ach part of the broken line is called an exterior side; and all the works constructed along any exterior side constitute a front or front of fortification . In the construction of fortifications since the use of gunpowder , two distinct designs of fronts have been employed : the bastion and the polygonal . — P B astion T race. The bastion front [ L I , Fig . 5] is sometimes called the French front from itsgeneral use in that country , although it originated in Italy in the l 6th century . It is based upon the flanking of the ditch from the parapet of the main work in its rear . The trace is constructed by bisecting the exterior side, AF , by a per pendicular G H , and making G H equal to i to l O f AF ; the two lines A H and F H prolonged are united by a line C D B DE parallel and equal to about i AF . The lines C and ° are drawn so as to make an angle of 100 with C D. The resulting broken line AB C DE F is the magistral of the B a B bastion front , of which A and E F are the f ces, C and

DE the flanks, and C D the curtain. The angles at A and t a h F are the salien ngles, those at B and E the s oulder n n angles, and those at C and D are the curtai a gles. The part of the work limited by the lines C B A B C is called a T A 1 R C E . 3

bastion . The two lines of the counterscarp I J and JL are drawn from the shoulder angles to the points I and L which are fixed by the desired width of ditch . The interior crest of the parapet M N O P QR is approximately parallel to the magistral . F rom the construction it is evident that if the flanks of the interior crest NO and P Q have the proper relief , fire delivered from them parallel to the superior slope may reach the bottom of the ditch along the line G H , and conversely , if the relief be fixed , the length of the cur tains may be modified to secure the same result . Then if the lines A D and C F , the lines of defense, do not exceed the close range of the flanking weapons , the ditch m ay be thoroughly swept from the flanks O f the parapet . In the bastion front as usually constructed , the exterior side was

360yards . As counterscarp galleries and armored caponiers can be protected more easily from the projectiles of the besieger ’s artillery than the open parapets or scarp galler ies of the flanks , the bastion front is no longer employed on the exposed fronts O f permanent works . P l a T — i o ygon l race. The polygonal front [P] . I , F g. 2] is also called the German front from its general application in that country although properly it had its origin in

France in the beginning of the 18th century . It is based on the flanking of the ditches from caponiers constructed in them . The magistral usually coincides with the exterior side A B ; the caponier is constructed at its middle point ; the counterscarp is parallel to A B , except in front of the caponier where it is broken so as to separate the caponier from the covered way ; and the interior crest of the parapet is also parallel to the magistral . The total length O f the front is usually from 1000 to 1200 yards and may be twice n the close ra ge of the weapons used in flanking the ditch .

The front may be modified as shown in P] . I , Figs . 3 and

4, by breaking the front into two faces , and placing the r - caponiers either at the salient or at the e entrant angles . ' In small works the ditches m ay be flanked equally well m fro the counterscarp galleries . Other advantages of the polygonal over the bastion front are th e great er N o\\xm a ex I 4 LAND DE FE NSES .

front fire , the smaller development of parapet , and the easier protection of the parapet from enfilade fire . — 0utworks. The outworks of any front are the separate defensive works which are constructed between the scarp of the main work and the crest of the glacis . They are utilized to increase the distance between the fortification and the investing lines of the besieger , to form a base for r sorties , to bring the foreg ound under cross fires which ’ enfil ade the besieger s trenches , to conceal the outlets of the main work , to mask all scarp walls , and to compel the besieger to fight for every inch of ground up to the scarp of the main work . On account of the great range and - accuracy of modern fire arms , many of the outworks have lost their value , and are no longer constructed .

Pl . II is a trace of an early work designed in accord T ance with the principles of the bastion system . h e out l works are A , the tenail e which masks the scarp wall of - the curtain and flanks ; B , the counter guard, a face cover m th C ravelin which asks e scarp wall of the bastion ; , the - or demi lune, which crosses its fires with the bastion face D and also covers the outlets of the main work ; , the ravelin - or demi lune redout, which is in the keep or citadel of the - m demi lune ; E , the tenaillon , a face cover which asks the - scarp of the demi lune ; F , the covered way of which G is r - ntrant lace o the salient p lace of arms, and H , the e e p f arms for a ssembling sortie parties to attack the works of the besieger . — A dvanced Works Advanced works are constructed beyond the crest of the glacis , but within close range , so that the outworks may assist in their defense . In Plate II , w r dans lunettes horn the advanced orks are e , , and I , a - m work. A crown workis an advanced work si ilar to a a c hornwork , in which two b stion fronts repla e the one of the hornwork . — d defen I nterior Works. I nterior works are a ditional m sive works constructed behind the parapet of the ain work . m In P] . II , K , is a cavalier, or high ound of earth constructed in a bastion to give a plunging fire on the foreground . INT E RIO R WO RKS . 1 5

Pl . III is the trace of a portion of one of the principal fronts of the enceinte, or interior line of the defenses of 1860and 1 Antwerp , B elgium , constructed between 864. It is designed in accordance with the principles of the 11 0 polygonal system , the exterior side being about 0 yards r B long . The outworks are A , the cove ed wag, , the ravelin with a reverse battery at C and a low battery at D to sweep - - the ravelin ditch , E , the counter guard or face cover which masks the masonry walls of the head of the caponier , F , the cap onier, whose casemated batteries sweep the main ditch of the front , G , the cavalier which gives a plunging n i fire on the foreground , and H , the defe s ble barracks , Which is the keep of the front and is surrounded on the interior by a palisade . In designating the difi erent parts of the front the terms face , flank , and curtain are used as in the bastion front ; thus I J is the face, LM and M N the

first and secondflanks, and N O the curtain . The parapet m along JK is called an orillon and serves to ask the flanks .

On account of the low site , the fronts of Antwerp are pro tected by wet ditches without masonry scarps . CHAPTER I I I .

D F N E S A S C O N ST R UC T E D B E T WE N 1 A N D 1 L A N DE E S E 870 880.

The remarkable results efi ected by the artillery in the - F ranco German war , led to a reorganization of the land defenses of many of the E uropean states . It was evident to the military authorities that all the principal fortifications of a country must be intrenched camps , and that a line of detached forts must hereafter be the principal line of defense . The first step was , therefore , the development of a type of detached fort which would meet the requirements of the new rifled artillery . The conditions which the new works were to satisfy m m were , a heavy ar a ent of guns well protected by traverse s from enfilade fire ; ample bomb-proof quarters and com munications for the garrison , and magazines for supplies during time of siege ; security against capture by open assault ; protection of all masonry from projectiles having an angle O f fall of — T ork P l an ] W s . d yp e of IV , represents the trace , P .

I , F ig. 1 is the profile of a fort developed by the Germans - just after the Franco German war , and employed in the defenses O f Strasburg , C ologne , Metz , etc . This type with slight modifications has also been employed in France ,

Italy , and Austria . — T race. The work is a lunette of which the faces are 2 m each 160yards , and the flanks , each 1 5 yards , easured ° along the magistral . The salient angle is 150 to re duce as much as possible the sector without fire , and to protect the faces from enfilade fire ; the shoulders are each to remove as much as possible the sector with out fire and permit each flank to sweep the interval between 16 T C H F O R T DE A E D s. 1 7

r the fo ts , and the approaches to the adjacent forts . T he gorge has a bastion front with a curtain of 60 yards and 1 faces of 55 yards each . These dimensions give a work which admits of a maximum artillery armament of twenty six heavy and six light guns ; nine of the former are on

each face and four are on each flank , well protected by

traverses . The garrison is about five hundred men . T he mm 2 co and of the work is 8 feet , which makes it conspic

uous, but gives it a wide field of view and fire . Ample m n quarters for the e are placed along the gorge , and m mm agazines for a unition , supplies , etc . under the rampart

of the faces , flanks , and the great central traverse . C overed

communications connect all parts of the work . The trav

erses instead of being made solid are hollow , and are bomb m n proof shelters for e , light guns , and ammunition . The fort is protected against capture by open assaul t by a wire m l entangle ent on , or in front of , the g acis, by a detached 1 scarp 8 feet high along the faces and flanks , by a full m scarp about the sa e height along the gorge , and by a masonry counterscarp 20 feet high extending entirely

around the work . The ditch is swept by eight or ten rapid

fire or machine guns , placed in a caponier at the salient

angle , in two half caponiers at the shoulder angles , and in - scarp galleries in the flanks of the gorge . A bomb proof guard-house is constructed in the ditch at the middle of

the gorge . Galleries for countermining operations extend from the counterscarp galleries at the salient and Shoulder

angles . The armament of the work comprises 15 c . m . and or 12 c . m . guns along the faces f use against the lines of investment and any visible works of the besieger ; siege howitz ers along the flanks for sweeping the intervals and approaches of the adjacent works ; field and rapid fire guns which are kept in bomb-proofs and in the course of the siege are moved upon the rampart for the near defense of the work ; and field or siege mortars to bring a vertical fire ’ on the besieger s trenches .

In France , the resul ts of the siege of Paris led to the m abandon ent of the bastion trace which h ad. A F N 1 8 L ND DE E SES .

of its system for several centuries, and the adoption of the t w R polygonal o all the ne works. e cognizing the difiicul ty n ara in tr n of defe ding the p pet both by fan y a d artillery , the F rench engineers attempted to separate the infantry and artillery in the defense . They accordingly adopted two types of works similar in outline to the German work but of greater depth . E ach had a large central traverse parallel to the front which formed a cavalier and also I a parades for the gorge . n one type this cavalier was re served for the artillery , and the infantry was assigned to the low parapet which encircled the work . This had the a of ecurin a mma advant ge s g good co nd for the artillery , but had the disadvantage of rendering the guns conspicuous n c r and thus increasi g the chan es of thei being dismounted . m in u r This type was also e ployed A st ia and Russia . I n the other type the low parapet of the faces was assigned nf to the artillery and the cavalier to the i antry . The posi tion of the artillery was thus concealed from the assailant a r r but it had the disadvant ge of ende ing dangerous , per cussion projectiles which struck the parados during the r artillery duel which p ecedes an attack . I n both types the casemated quarters were under the cavalier. E ventually both types were abandoned for one similar to the German fort consisting of a single parapet . — I nterior Lina The German engineers were not ready to abandon the inner line , and in their new works they either retained the old lines or constructed new ones . A ll u u of new lines were s ally continuous lines polygonal fronts , like the front of Antwerp , but without its elaborate out works . These were limited to the caponier which was m thoroughly protected from distant fire , even by ar or if

f . T necessary, and a ravelin in front O the gateways he counterscarp was revetted to a height of twenty feet , but there was no scarp revetment of any kind . In the F rench r no works, the old lines of works we e left but new ones

were constructed . — m E xamp le. Strasburg may be taken as an exa ple of an intrenched camp constructed between 1870and 1880.

S 2 0 LAND DE F E N ES .

- il m n l and one fourth m es fro the i ner ine , and one and one - half miles from fort II . B eing in a re entrant angle . be te tween II and IV and pro cted by the Soufi el , it is smaller - than the adjacent works . Fort IV is three and three fourth miles from the inner line and less than a mil e from fort r r m I I I . It is on the no thern ext e ity of the important ridge northwest of the city , and occupies a commanding position fi behind the Sou el . B eing a salient it is a strong work .

The west front is protected by forts IV to VIII . F ort V is three miles from the inner line and one mile from fort IV . It is a strong work which occupies the most H u commanding position on the a sberg ridge , and has good. n command over all the cou try in its front . F ort VI is m n mil three miles fro the in er line and one e from fort V . It is a strong work which occupies the southern end of the r r Hausberg ridge . The th ee fo ts IV , V and VI may be considered as the key point of the defense , as attack along any otherline would not give the besieger a decisive victory or the possesion of a point from which he could successfully - attack the inner line . F ort VII is two and one half miles from the inner line and one and three-fourth miles from fort VI . It is a strong work which closes the gap between fort VI and the B ruche canal and creek . F ort VIII is two and three-fourth miles from the inner line and two and - one fourth miles from fort VII . It is a strong work which B commands the plateaubetween the ruche and the Ill , and the lines of communication which cross it .

The south front is protected by forts VIII to XI . F ort IX is three and three-fourth miles from the inner line and - B n two and three fourth miles from fort VIII . ei g built in a swamp it is similar to fort I and has wet ditches without r - m ditch defenses . Fort X is fou and one fourth iles from the inner line and two miles from fort IX . Like fort IX it

has wet ditches without ditch defenses . F ort XI is five miles from the inner line and two and one-half miles from

fort X . It is similar to forts IX and X being constructed

on marshy ground along the banks of the Rhine . This fort is placed far from the inner line because of a heavy A B ' ST R S UR G . 2 I wood extending along the Rhine in its rear; it was deemed advisable to advance it beyond the wood . The works on the south front are not so important as those on the north and west , as a belt of country over one mile wide between the I I] and the Rhine can be inundated .

This inundation is just outside the inner line of defense .

The east front is defended by forts XI I , XIII , and XIV on the east bank of the Rhine , and two small forts near the east abutment of the railway bridge . F ort XII is three and three-fourth miles from the inner line and four and - three fourths from fort XI . B eing in a marshy position it has wet ditches which are flanked by a small ravelin at the salient and half caponiers and scarp galleries . F ort XI II is three mil es from the inner line and two miles from fort

XII . It is similar in construction to that fort . F ort XIV - is two and three fourth miles from the inner line , two miles - from fort XIII and three and one half miles from fort I .

It is similar to forts XI I and XIII . s As an accessory to the outer line of defense , there i the strategic railway connecting the principal forts . This road leaves the M olsheim line behind fort VIII and joins the Germersheim line after passing about one-third of a mile in rear of all the forts of the sector between the B ruche and the lower Ill . Another line leaves the B ale line near fort IX and connects with the canal from the Rhone to the

Rhine near fort X . The communication thus formed um r parallel to the outer line of defense , with the n e ous highways and railways that radiate from the city , indicate that the Germans have considered with great care the necessity of lines of communication between the inner and outer line of defense . — I nner Lina The exact date of the original construction O f the inner line of Strasburg is unknown ; about the middle of the 16th century it was reconstructed by the

German engineer Speckle , and was remodelled by Vauban when the city was taken by the French in 1681 . T he in terior line had its longer dimension east and west ; and its i ine was east end terminated n a Strong citadel . The l 2 2 LA ND DE F E N SE S

m co posed of bastion fronts well supplied with outworks. l r To a low for the g owth of the city , the Germans removed the entire northern and western fronts and construc ted n ew ones much farther out. The O ld south front still re mains as constructed by the French . w The ne trace (Pl . V) starts from the at a point to the south of the city , forms a semicircle with its convexity turned to the northwest and returns to the I I] at a point north of the city . It then crosses the Ill , makes a turn on the right bank and extends to the canal from the M arne to the Rhine , which it follows for five hundred feet to envelop a park called the Orangerie . It then turns sharply to the south and follows the left bank of the lesser branch O f the

Rhine to the old citadel , which has been preserved . Throughout the west and northwestern part the trace is polygonal with armored caponiers protected by ravelins ; in the north the inner line is simply a parapet covered by

a wide wet ditch . The O ld citadel , included in the new inner line , is only a strong point of the line , and can hardly be depended upon as a keep in case of attack . ’ ' — R esume. Strasburg is an example of intrenched camp constructed in accordance with the views of military engi - neers in Germany after the Franco Prussian war . The Site being nearly level , the distances between the forts and the main work were made to depend upon the range of the existing artillery and the tactical considerations governing attack and defense . It is probable that the works have been somewhat modified since the introduction of s hells containing high explosives ; the caponiers attached to the

scarp have been replaced by counterscarp galleries , the roofs of all casemates and bomb-proofs have been strength - u m n ened , at least one half of the g ns fro the forts have bee u removed to annexed batteries , and a few t rrets have been u constructed for rapid fire and 15 c . m . g ns .

If threatened by an attack , the garrison of Strasburg would probably be at least men ; its armament would comprise about 450 heavy , and 200 light pieces besides war those used to flank the ditches . In time of the per B ST RAS URG . 2 3 manent defenses would be supplemented by field works and trenches connecting the detached forts and extending the zone of operations a mile or so to the front of the works. At the time of the F ranco-German war there were no detached forts , and although both the garrison and the de n fe se were in a bad condition, the Germans after failing to reduce the place by bombardment were compelled to resort to a regular siege . The city was not surrendered until the assailants had made a breach in the main work and were f ready or the final assault . rr — B a ier F orts. The barrier forts constructed between 1 7 8 0and 1880, especially on the eastern frontier of F rance , do not differmaterially from the detached forts of intrenched camps . As a rule they belong to the type of forts with a. central cavalier . CHAPTER I V

D L A N DE F E N SE S SIN C E 1880.

The development of siege mortars and howitzers whic h 1869 m u r 1 began about had ade s ch prog ess by 880, that serious doubts began to be expressed as to the value of open defenses. In experiments conducted at M eppin in 1 21 882 with a c . m . siege mortar , fifty per cent of the shots were placed in a rectangle x 13 yards at a range of 1000 r 4 x 26 2200 ya ds , in a rectangle yards at a range of yards , 7 x 4 and in a rectangle 0yards at a range O f two miles . At f a range O about one mile , five shrapnel shots produced 1439 hits in a horizontal target 109 yards wide and 164 yards deep . F rom these and similar experiments it became evident that the barbette gunsof the works constructed between

1870and 1880, could not be manned after the assailant os tablished his mortar batteries within effective range of the forts . This was followed by the use of high explosives in shells , or the introduction of torpedo shells , between 1883 and 1885 . The first authentic accounts of their effects were published in 1886 ; the results of experiments made at M a] i 21 m . m n 70 maison , F rance , with c . ortars contai ng pounds of melinite . One shot struck a masonry caponier whose walls were feet thick and whose arches were covered ar sh t m with 10feet of e th . The q penetrated and al ost de r mmu stroyed it . A second shot dest oyed an arched a nition 1 chamber covered by 4 feet of masonry and 3 feet of earth . A third shot penetrated the covered way j ust in front of 4 the counterscarp wall and blew down 0 feet of that wall . This fort was constructed of ordinary brick-work such as 24 F R 'r 2 ARMO RE D O s. 5

was used in most of the continental fortifications. The introduction of the mortar Shrapnel and torpedo shell made it necessary either to protect the guns by

m . armor, or to remove them wholly fro the works The latter solution was generally adopted in Germany and

F rance ; they were mounted in the intervals , generally in annexed batteries close to , and under the protection of the m forts . The latter became infantry redouts% It also beca e necessary to remove or strengthen the caponiers , detached - ni scarp walls, and bomb proofs . The capo ers were gen orally removed and replaced by counterscarp galleries , the detached scarp walls were replaced by iron fences or - E x eri barriers , and the bomb proofs were strengthened . p ments having shown that a bed of Portland cement con crete 5 feet thick would resist the penetration of single mortar shells , this concrete was used to reinforce the arches and walls previously constructed. In new works , concrete was the only material used in the construction of masonry . E xperiments also indicated that a covering of earth less ff than sixteen feet , acting as a tamping , increased the e ects of explosion ; a thickness of three feet however added little to the explosive effect and prevented the scattering of splinters which would result from the projectile striking a bare wall . — l B A rmored F orts . General B ria mont of the elgian engineers was of the opinion that artillery could no longer be maintained in open batteries either within , or without , the works . He therefore advocated securing the desired protection for the artillery , by placing it in armored turrets , or behind armored shields . In the year 1882 the Rouman ian government decided to fortify its capital , B ucharest , B and engaged General rialmont to design its defenses . use m The first extensive of ar or , was made in these works . The system adopted by General B rialmont is now known as that of armoredforts. — P l F ort with Keen . VI . This is of the general form of the German fort , although deeper , and has about the a same development of front . The profile and trace Show 2 6 LAND DE FE N SES . dry ditch 20yards wide with an earthen scarp and counter a scarp , an iron barrier on the faces and flanks , and r masonry sc arp along the gorge . The ditch is swept f om e a caponier at the salient angle , two caponiers at the should r angles and two scarp galleries in the flanks of the gorge .

‘ The ditch of the keep has masonry scarps and counter scarps swept from counterscarp and scarp galleries . The parapets on the ‘ faces and flanks have a minimum thick m ness of 20yards , and on the gorge 5 yards . The co mand varies from 32 feet along the faces to 23 feet along the 1 gorge . The principal armament consists of six 5 c . m . guns in three turrets , one near each shoulder angle and one in the keep ; two 21 c . m . howitz ers under Shields , one on each face ; one 12 c . m . howitzer under a shield in the r salient ; six c . I n . rapid fire guns in disappearing tur ets , four at the four angles of the main work and two in the B keep . esides these , barbettes are arranged for field guns on the faces and flanks , and an infantry parapet along the gorge and along such parts of the faces and flanks as are not occupied by artillery . B efore the works had been ff actually begun , the e ect of torpedo shells was ascertained , and to resist their destructive effects , all arches exposed to curved and vertical fire were made of concrete six to eight feet thick . Otherwise the underground constructions m l are Si i ar to the German fort . The keep in this work forms the second line of defense ; most engineers differ from General B rialmont and consider the keep of little value as compared to its cost . — F ort Without a Keen The otherforts of the defensive 1 line are quadrilaterals of the type shown in P] . VIII , Fig . . The front of this work is only 110 yards and the depth 80 m r yards . It has a ditch 9 yards wide with a asonry sca p along the curtain of the gorge . The ditch is flanked by

fire from counterscarp galleries and disappearing turrets . The command of the work is only 13 feet and the thickness of the exposed parapets 26 feet . The armament consists of

four 15 c . m . guns in two turrets on a central traverse t c 2 r s parallel o the fa e ; two 1 c . m . howitzers unde shield

2 A F 8 L ND DE E NSE S .

1 12 21 5 c . m . guns , four c . m . guns, two c . m . howitzers , 12 two rapid fire c . m . howitzers , four c . m . rapid fire guns all in turrets or under shields . One Side of the gorge Shows a casemate battery for sweeping the interval between the forts . Though the type given is triangular , no fixed rul e was adopted , and some of the works were made with more sides when the features of the site required it . The armor used by General B rialmont was in the form of turrets and shields . - ' — T urret for two 1 5 c . m. 2 5 C alibre G uns I n 1885 experiments were made in Roumania to test two types of turrets , one of a mushroom form and the other of a cylindrical form , which had been purchased by the R ou manian Government . As a resul t the mushroom type turret shown in P] . IX was adopted . As manufactured by u the Gr son works of Germany , the armored top of the turret consists of three plates of inch rolled wrought iron screwed to a Skin consisting of two thin plates of steel riveted together . The armor is carried by a cylinder of plates and angles about 16 feet in diameter and 8 feet high . The cylinder rests upon a horizontal circular plate ; this is supported by a ring of small steel conical rollers which run on a circular track . The glacis is made of a number of voussoirs of chilled cast iron set in concrete . The entire turret is set in masonry , in which are formed the magazine , loading rooms , etc . The total weight of the turret without guns is 248 short tons , or with its guns about 251 tons . one oflice The service of the guns and turret requires r, m en one gunner, and four m en to serve the guns , two to bring up ammunition , and four men to revolve the turret . A complete revolution can be made in one minute and the elevation of the guns changed one degree in three seconds . At B ucharest this turret was exposed to the fire of three 15 c . m . guns at a range of 1100 yards and received

36 hits without serious injury . One hundred and sixty m five rounds were fired at it from two 21 c . m . rifled ortars at a range of 2700 yards without hitting it . The turret H 2 T URRET S AND S IE LDS . 9 then received 33 more shots with re duced charges from the n 15 c . m . gu at a range of only 60 yards , and although v ery much damaged it was declared stil l serviceable to ’ p rotect its guns and interior mechanism . After one day s repairs the guns were mounted and the turret was found to revolve with ease . This armored turret may , therefore , be considered as proof against ordinary heavy siege artil lery . Similar turrets are now made in Germany of chilled c ast iron , and in France and B elgium of wrought iron and steel . A smaller turret of the same type is also made for

12 c . m . inch ) gun s . The gun carriages are of two - c lasses ; the minimum p ort as shown in P] . IX , and the - non recoil , in which the recoil is communicated to the m turret by a muzzle ring on the gun . In those ade for the defenses of the M ouse it was specified that the muzzle of the guns must not project outside the turrets . Turrets are also made for single guns as these are preferred by some artillerymen . — Shield for 2 1 c . m . Howitzer. The Shield for the

21 c . m . howitzer is as shown in P] . X . The construction of the overhead shield and glacis does not differ materially from the roof and glacis of the turret . The shield is con nected by angle irons to two steel transoms a, which act as the checks of the gun carriage and are united by a cross transom , b. The transom , b, rests upon a vertical m shaft , c . The recoil of the howitzer is co municated by the transoms and angle irons to the shield which ordi narily rests directly upon the glacis armor . A simple device allows the weight of the gun and shield to be transferred to the shaft when the gun is to be traversed . The motion of revolution is given by a pair of levers or a ratchet wheel . The service of the howitzer and turret requires four m en to serve the howitzer and rotate the tur ret , aud two men to raise and lower the shaft . The total height of the chamber is about feet and its diameter

feet . Similar shields are constructed for the ordinary

15 c . m . , and the 12 c . m . rapid fire howitzers . 0 3 LA ND DE FE NSE S . — Disapp earing Turrets. A disappearing turret as manu factured for the or c . m . rapid fire gun , is as

Shown in P] . X . The overhead Shield and glacis armor are constructed as in the turret and howitzer shield , but of less resisting power . The shield rests on a low cylin der of cast steel plate . The weight of the whole is transmitted to the central shaft by means of two strong transoms as in the howitzer turret . The shaft itself rests on a counter m poised lever by eans of which it is raised and lowered . The gun is supported on horizontal rails which allow it to be withdrawn into the turret when the latter is to be lowered . The service of the gun and turret requires only two men . The total weight to be lifted is about 12 short tons. — A rmored F ronts. Lieutenant C olonel Schumann of the German E ngineers , who devised the turrets and Shields u the com an 1 - manufact red by Gruson y y , about 885 87 , originated a system O f fortification which has been styled the system of armored fronts. This system has been adopted by the Roumanian Government for the defense of F three places , oksani, Nemolassa, and Galatz on what is known as the Sereth line of defense against invasion from - the north east . ’ The guiding principles of Schumann s sytem were to avoid the great intervals between works of the prevailing systems , and to provide a maximum amount of fire from small calibre guns . His works were all simple batteries

Open at the gorge arranged in two or three lines . At Fok sani the arrangement is in three lines ; the first line has - forty one works ; the second and third each fifteen . The interval between the works of the first line is about 500 Mfl yards, and of the others a little less than this distance . The distances between the lines is approximately r 500 yards . In the first line , the wo ks are barbette bat terice of seven c . m . inch) rapid fire guns in trans portable turrets (P l . XI , F ig. The second line consists 12 m of six c . m . in disappearing turrets , one c . . gun in

2 m . m rt r . a disappearing turret , and two 1 c . o a s , ( Pl XI , T R T A N D H I : U RE S S E LDS . 3

F ig. I n each work of the third line there is one 12 m z r c . . howit e and four to six c . m . guns . (Pl . XI ,

F ig. The profil e employed in the construction of the batteries is the triangular profile with Shallow ditches , planted with thorny bushes twisted with wire , or filled with wire entanglements . (Pl . XI , F ig. — T ransp ortable T urrets. The transportable turret in v ented by Lieutenant C olonel Schumann is shown in P] . XIII ; the roof is of cast steel inches thick which makes it proof against small arms and shrapnel . The total weight of the turret with its gun is from to tons , depending on the calibre of the gun . These turrets are manufactured for the c . m . , the c . m . , and the

c . m . rapid fire gun . — M ortar Shield The mortar shield is shown in P] .

XII . It consists of a breech loading mortar buried in a Spherical steel casting which is supported on a revolving vertical shaft . ’ The objections to Schumann s system of defense are that it divides the defenders into a great number of small squads not easily controlled , and that it leaves no sphere of action for infantry cooperation or active defense . or r — Works f N ea and Distant Defense. B esides the systems of great armored forts of General B rialmont, and

O f armored fronts of C olonel Schumann , there is a third system of defensive works favored by engineers who do not believe in such an elaborate use of armor on account % of its cost .

It is known as the system of near and distant defense. These engineers recognize that guns cannot be kept mount ed in barbette in a fort when the besieger once opens fire with his howitzers and mortars , but they do believe that the heavy guns can be kept in barbette or embrasure batteries in the interval between the points of support if concealed by the folds of the ground , hedges , or other masks . They believe that the works upon the points of support should

T he cost of the de ense of the M ouse inc ud n the urchase of and was f , l i g p l o er 000 v . : 3 LAND DE FE NSES .

m i l be a n y for infantry and movable guns ; if , however , the location is one that commands the surroundings and has

no other good site in the vicinity , one or two large guns ma m y be placed in the work either per anently in turrets , or temporarily in barbette to act simply against the line O f m invest ent , and to be withdrawn when the siege is begun . A few rapid fire guns in disappearing turrets are allowed

in the redouts to assist in the near defense . In this

system the intervals between the works , about one to one - and one fourth miles , are usually swept by the fire of howitzers in masked batteries at the gorge of each near

defense redout . - — N ear Defense Works. The simplest redout of this k B ] : ind is the type adopted in the ritish service , P XII I , m - m known as a se i per anent infantry redout . The trac e of the interior crest approximates to a rectangle with rounded ends whose extreme width is 93 yards and extreme depth 40 yards . The triangular profile is employed and the work is protected from assault by an iron barrier and m wire entangle ent which extends entirely around the work . Under a central traverse are bomb-proofs for the troop s who ordinarily camp outside the work ; these bomb-proofs mm have a covered co unication to the parapets of the faces . The parapets have a low command and are designed to protect the men in their rear from shrapnel fire . The in fantry defense is strengthened by two rapid fire guns in m disappearing turrets . In very i portant places both the size of the work and the number of disappearing turrets are increased . h On the continent , these redouts usually ave masked casemate batteries similar to caponiers in the gorge . These % ” are known as traditor batteries , and replace the guns in the flank for sweeping the intervals between the works . The principles governing their field of fire as designed by orduin m n C olonel Vo of the Dutch ar y , are as show in P] .

I , Fig . 7 . The forts are small redouts placed at intervals 12 of 2200yards and have an artillery armament of two c . m . guns in a turret for front defense and distant fire , Six I T T NE AR AND D S AN DE FE NSE . 33

sm aller guns or howitzers in the % traditor battery along f r the gorge o flanking adjacent works and the intervals . r di s m These t a tor batterie are entirely asked by the work , from the view of the enemy in the angle of front fire . For near defense the infantry is assisted by rapid fire and m achine guns in barbette . The work is protected from assault by a wet ditch and wire entanglement and , as the turret gun is used only for distant fire , it is concealed from the besieger in the foreground by the parapet in front . In Russia the supporting points are occupied by closed redouts of large dimensions with well flanked ditches of triangular profil e . These works admit of individual defense by infantry and by movable rapid fire and machine guns . % ” The intervals are swept by traditor batteries . As no t turre s are used , the heavy artillery armament is in open m batteries constructed in the intervals . In Ger any , Austria , and France , the forts in existence have been converted in - a m to near defense works for inf ntry and achine guns , proof against modern siege artillery , by replacing the caponiers by counterscarp galleries , and by removing most of the heavy guns into annexed batteries outside , but under the protection of the redouts . Usually one or two of the heavy guns are left in the work but are placed in turrets . The latest designs of military engineers show apref erence for closed redouts with a triangular profile , contain ing one turret for heavy guns and several disappearing % turrets for the machine guns , with traditor batteries

sweeping the intervals . All the works contain ample - bomb proof quarters , magazines , and communications for the artillery and infantry garrisons , and differ only in the m minor details of the nu ber of guns , shapes of works , and % manner of constructing the casemates - — i n D ns Works . for D sta t efe e These are batteries guns , howitzers , and mortars . The guns usually employ direct and the other pieces indirect fire . For direct fire the guns m m m ay be either in fixed , or in ovable , e placements . Fixed emplacements are batteries laid out and constructed in time of peace . As an enemy could soon sil ence a fixed F 34 LAND DE E NSES .

battery Whose location was known, care is taken to conceal this location as much as possible , by the irregularities of n u c the site , or by at ral and artifi ial masks , and to dis tribute the armament as much as possible by plac ing only two or three guns in each battery . Disappearing gun are m l m ur ] carriages e p oyed for the sa e p pose . P . XIV , shows the type of a two gun battery employed in the h B ritish service . To protect t is battery from capture by

O pen assault , it is placed several hundred yards in rear of t l u the line of redou s , and , if not safe y g arded by infantry , m is surrounded by a wire entangle ent . Guns in movable emplacements are guns on flat cars which move on a rail way in rear of the line of redouts ; such a mounting has

‘

been constructed in F rance [P] . I , Fig . It woul d be impossible to silence a gun thus mounted except by a

chance Shot . Howitzer and mortar batteries are concealed by the folds of the ground which , while they do not interfere with r curved and vertical fi e , allow the construction of observ for v ff atories near by , obser ing the e ect of the shots . — B arrier F orts. A barrier fort must be safe against capture by O pen assault or bombardment , its guns must be

mounted so that they cannot be easily silenced, and the work must have an ample water supply and bomb-proof magazines for provisions and ammunition , so that the work cannot be taken by investment during the ordinary dura

tion of a war . These conditions require that the work be

surrounded by an obstacle in the shape of a deep , wide ditch thoroughly flanked by the fire of machine or rapid u m and fire guns , that all g ns be protected by ar or , that - and ample bomb proofs be provided for troops supplies . T wo barrier forts have been constructed recently by

the Germans at M olsheim , in the foot hills of the Vosge s m l ur r mountains, about 12 i es west of Strasb g ; whe e the u il in A S u only north and so th ra way lsace west of trasb rg, connects with an east and west line running from the

F rench boundary to that city . The works are of the same n r r r o in M u ge e al cha acte as th se the defenses of the e se ,

F 36 LAND DE E NSE S .

front over which the assailant can make an attack . These m can be utilized only when a strea runs into , or parallel to , the front of some part of the line of defense so that the dams may be kept under the protection of the forts . CHAPTER V

P R IN C IPL E S O F L A N D ° DE F E N SE IL L UST R A T E D B % T H E F O R T I F IC A T IO N S O F F R A N C E O N T H E

G E R MA N F R O N T IE R .

The selection of the points to be fortified is made by the military authorities of a nation , and conforms to the m n general sche e of defe se , or to the plan of operations of the land forces to resist invasion either by offensive or defensive measures . In some countries there is a per m anent commission for this purpose designated the C om m ission of National Defense . — hi Scheme of Defense The scheme of defense , w ch determines the location and character of each permanent fortification depends upon the organization and efficiency i of the armies of the defender and probable assa lant , as well as their allies ; the configuration of the boundary ; the topography of the boundary and adjacent territory ; the location of the existing and projected lines of transport and supply ; and the location of the political and commer ciel centres of the country . — E A rmies. N early every continental power of urope has now adopted the system of universal service , and every able bodied man is enrolled either in the active army , or r in one of its reserves . The milita y strength of a nation has , therefore , become approximately proportional to its population . In the future a small nation without allies can no longer meet a large one in the open field , but must resort to fortificatio n to strengthen its forces in the future struggle for national existence . The fortifications must be permanent , for each great nation now maintains so large a standing army that a small one would be overwhelmed be 37 38 L A S D om fore She had time to organize an adequate system of field struc ted since the F ra nco -G erm an war by th e small states f E uro B e ium Hc-Lan- De mar R o pe , lg , L n k, oum ania , and wi rland whic no on r w S tze , h l ge trust holly to guarante ed an doubtful all an neutrality d i c es . T he great nations maintain in their peace establish me ts onl a frac tion of their avai a e m en th f n y l bl , ere ore , it will take tim e to m obiliz e their armies and transp ort them t t r to the threa ened fron ie . During this time every avail able railway will be worked to its utm ost capac ity by the t r ties an an n military au ho i , d y i terference by the enemy woul d be more or less disastrous. T o prevent this inter it is usua to c nstr ct l n f ference l o u a i e o fortifi cation , or a t nc ed cam near th w great in re h p , e fro ntier hich m ay be ’ a a i st nvade used as base ga n an i r s raiding parties . Under existing conditions a nation can onl y neglect those frontiers w which separate it from nations hich are weak , or which are certain to be either friendly or neutral . — B oundary T he form of boundary which separates a country from its possible or probable adversaries has an u n the a vas n n important bearing po pl n of in io , a d therefore upon the scheme of defense . If the boundary be app roxi mately a right line , its form gives no advantage to either

Side ; it is otherwise , however , if the boundary form s a - salient or re entrant angle . If we consider a possible war between Russia and the allied powers of Germany and t m u r Austria , it is probable hat the allied ar ies wo ld be fi st ul i di mobiliz ed , and wo d have the option of nva ng Poland from the south and west , north and west , or from the to off r north , south , and west so as cut and dest oy the Russian army which now occupies that province with n headquarters at Warsaw . To meet this conti gency , R us siamust eitherwithdraw her army and temporarily abandon mu m n Poland , or she st protect this ar y in an i trenched region until her other armies can advance to the support d c m r a m of its flanks , an o pel the etre t of the ar ies which n u threaten its communications . A war betwee R ssia and P C P O F RIN I LE S DE FE NSE . 39

G erm any would place the German force in E ast Prussia in the same predicament . r h — T op og ap y . I f the boundary be a range of high m n ountai s with few passes , as the Alps in E urope , an in vader may be checked temporarily by the construction of s trong works in these passes ; if the boundary be a wide , d v eep ri er , with few bridges , strong works commanding the bridges will have the same effect . If the mountain c m hain , or river be so ewhat removed from the boundary , t bu is generally parallel to it , as the C arpathian Mountains f o Austria , and the Rhine river of Germany , by fortifica t ion at the passes and bridges , these obstacles may be c onverted into lines of defense and bases for offensive m m m ove ents . If the ountain chain or river be p erp endic ular instead of parallel to the boundary , the fortifications c onvert it into a screen , from which offensive movements m ay be made against an invader who advances on either side , parallel to it . L o T r n — ines f a sp ort. Modern armies on account of their great size , require the use of all railways in their rear i m for the r aintenance and supply . Invasion along any line of railway may be interrupted by the construction of m m a fortification to guard so e i portant bridge , tunnel , or junction where the route cannot be easily diverted . — P olitical and C ommercial C entres While it is true m that the defending ar y , and not its capital , must be the true objective of the invading force it is equally true that any interruption of the machinery of government will ser i usl m aras o y e b s the defender . Unless the political capital is secure against ordinary attack , the defending army will , in its retreat , endeavor to interpose itself between the in vader and that capital , and may thus be seriously em i harassed in ts movements . For this reason it is usual to surround the capital with permanent fortifications , partic ul arly if this capital be near a dangerous frontier . In some countries , the political capital being so located as to be ffi ul m di c t to defend by the ar ed strength of the state , a commercial centre is selected and fortified with a view to 0 D 4 LAN DE FE NSE S . its us as c e the political apital in time of war . Antwerp is m B m B the intrenched ca p of elgiu , instead of russels , be - cause being a sea port , it is less easily invested by a land m force , and is ore easily relieved by friendly powers .

T H E F O R T I F I C A T I O N S O F F R A N C E O N T H E G E R M A N

] B oundary . [P . XL] The common boundary of France and Germany , as fixed by the treaty of peace after the - Franco German war , begins on the Swiss frontier about - twenty five miles west of the Rhine river , thence runs almost n n parallel to the Rhi e , to a poi t thirty miles west of Stras burg ; thence it runs in a northwesterly direction to a point about eight miles west of the Moselle at Metz ; thence it runs L n northward to the uxemburg fro tier . The total length of this boundary is one hundred and seventy miles , of which — only fifty miles follows a natural barrier ; viz . the crest of the Vosges mountains north of B elfort . The railways which cross the frontier and connect Paris with the Rhine — — — are l st . Paris Laon or Reims Mezieres Diedenhofen — — 2 ( Thionville ) Treves C ologne or C oblentz . d. Paris m — — — m m Rei s Verdun Metz Mayence or Ger ershei . 3d. — — — — Paris Nancy Strasburg . 4th . Paris Langres B elfort — Mul hausen . While no railways cross the Vosges m oun tain boundary , there are several branch lines which reach the foot hills on either side ; their termini are connected by good highways. The principal railways , parallel to the frontier , are those following the valleys of the Meuse and

Moselle . National highways follow the lines of all the great railways ; departmental and smaller highways form a complete network of good lines of communication p erp en di ul r c a . , and parallel , to the frontier The frontier rivers , the Moselle and the Meuse , both run parallel to the boundary ; neither can be considered a serious obstacle , as — they are not navigable above the Verdun Metz railway . W S est of the Verdun valley is the great basin of the eine , in which all its tributaries flow toward Paris , and thus form natural lines of invasion . South of the sources of T I FO RT IFIC A IO NS O F FRANC E . 4

the M oselle and M euse is the basin of the Sadne, one of the great tributaries of the Rhone . E ast of the boundary is the German intrenched camp of Metz and the great mili tary base of the Rhine , protected by its numerous fortified bridge heads , C ologne , C oblentz , Mayence , Germersheim ,

Strasburg and B risach . It is thirty miles from the Upper

Rhine to the frontier south of Strasburg , and from thirty to one hundred and twenty miles from the Rhine to the frontier between Strasburg and C oblentz . F rom Metz to - Paris is only one hundred and seventy five miles . - The F ranco German war , which deprived France of the Rhine as a boundary above Strasburg , and of her principal eastern fortifications , Metz and Strasburg , placed her in a very disadvantageous position to defend her terri tory should another war break out before her military system was wholly reorganized . E ven with an equal land n force the defensive li e , and offensive base of the Rhine m would give Ger any a great advantage in any future war . m To restore the equilibriu between the two powers , F rance , immediately after that war , adopted the universal service n m system i her ar y and began to fortify her new frontier . The war demonstrated that the old fortification with outworks and advanced works , no longer protected the cities about which they were built ; many of the old forti fied cities were therefore wholly abandoned by the military authorities . As the intrenched camps of Metz and Paris were taken by investment alone , the fortification of the new lines were so enlarged or combined as to make a com m plete invest ent almost impossible . — Lines of Defense Assuming that Paris would be the ultimate objective of any invasion , it was decided to organiz e the defense in three lines ; a frontier line m which would check invasion and cover the obilization ,

assembly , and first deployment of the field army ; an intermediate line which would cover the assembly of the territorial troops and afi ord a refuge to the field armies should they be compelled to retreat ; a strong line about

the city of Parish which , on account of its social and 2 D F N 4 LAND E E sns .

political value , was to be the citadel of the defense as in

former wars . — F rontier Lina As previously stated the onl y natural

lines of defense , on or near the frontier , are the Vosges mountains , the Moselle , and the M euse rivers . As the German army can assemble in Lorraine west of the range n of the Vosges , a li e along this range could be readily turned and would soon be untenable . The Moselle too runs into German territory and in itself offers no secure position for the left fianknorth of Toul . The Meuse form s

a good line north of Toul , but is too far distant from the boundary south of that place . After careful examination a line was adopted which combined the best features of each of these lines . This line begins on the north at the B elgian frontier and follows the Meuse to Toul , thence along the Moselle to its headwaters in the Vosges moun tains . The right flank is prolonged to the Swiss frontier , B via elfort and Montbeliard as will be explained hereafter . m The line is nowhere ore than forty , nor less than twenty miles from the boundary and therefore leaves but a nar f row belt o country without protection .

To fortify this entire line , one hundred and sixty miles m long , would not be advisable either fro a military , or from a financial point of view ; hence the French C ommit tee of National Defense divided it into four intervals , two i v u u of which are fort fied so as to lea e no road ng arded , and two of which offer little or no obstruction to the

passage of an enemy . The fortified intervals are called m curtains , and extend fro Verdun to Toul , and from

E pinal to the Swiss frontier .

The northern interval , fifteen miles in extent , between B m Verdun and elgiu , is left open because the communica a m tions in this section lead aw y fro the objective , and m because a hostile ar y operating in this narrow space , t wi h a neutral territory on the one flank , would be in a

dangerous situation . On the railway near the B elgian frontier the old fortified place of M ontmedy is left as a

temporary barrier fort .

44 LAND DE F E NSE S .

m nected by curtains , and a citadel ; the peri eter of the - outer lin e measures twenty four mil es . One barrier fort to the north closes the gap between the Vosges mountains

and B elfort , and five barrier forts close the gap between i B elfort and the Swiss frontier , about nineteen m les dis tant . The French armies , assembled behind these curtains and the B elgian frontier , will be in a good position to act offensively against the flanks of any hostile armies which

attempt to penetrate the intervals . If the French field armies invade foreign territory the reserves would occupy these curtains and transform them into a secure base . — I ntermediate Line I fa hostile army succeeds in pass w ing the frontier line of defense , it ill find itself in the basin of the Seine , and will naturally follow down one of the numerous tributaries whic h lead in the direction of

Paris . In the north , these are the Oise , the Aisne , and the

Marne . To check an advancing hostile army , the great plateau between the Oise, the Aisne , and the La Fere Laon-Reims railway has been converted into an intrenched region . An intrenched camp at La Fere is connected t with the A isne , eigh een miles distant , by five barrier forts constructed near the eastern edge of the plateau . La Fere is a double bridge head of eight forts and an inner line ; w - m the perimeter measures t enty four iles . B etween the Aisne and the Marne is the intrenched camp of Reims con sisting of ten forts and several batteries without an inne r m -five line ; the perimeter easures forty miles . The north m e m ern forts are six il s fro the Aisne , and the southern , seven miles from the Marne . A great forest occupies the space between R eim s nd he Marne . A barrier fort com E t mands the defile of through which passes the Paris

Strasburg railway , the Marne , and a national highway . S In the south the tributaries of the eine are the Aube , m n the Upper Seine , the Ar a con and the %onne . A hostile n army , which passes the southern curtai will reach these rivers as well as the valley of the Rhone , by passing m L through the triangular territory li ited by angres ,

B esancon , and Dijon . This territory has been converted H FRE NC LAND DE FE NSE S . 45 into an intrenched region by making the three vertices intrenched camps . Langres has nine exterior forts , four intermediate forts , and a citadel ; the perimeter of the exterior line measures thirty-three miles ; its forts com B m and all the railways in the vicinity . esancon , fifty m iles from Langres , has nine exterior forts , six intermedi ate forts , and an inner line ; the perimeter of the exterior line measures twenty two miles , and forms a double bridge - head on the Doubs river . Dijon , on the Paris Lyons rail - r - way , thirty seven miles from Lang es and forty two miles from B esancon , has six exterior forts , one intermediate fort , and an inner line , the exterior perimeter measures - twe nty four miles . A hostile army attempting to invest any of these places would find its rear threatened by the forces occupying the others as bases . This region has good railway and highway connections with Paris and the south of France . — F erris The intrenched camp of Paris has been en l arged since the Franco-German war by the addition of a n ew exterior line . At present it consists of an exterior line of works , consisting of three curtains on the perimeter - of a polygon seventy two miles long , and seven and one half miles from the city . There are two undefended

intervals of nine miles in this outer line , and one of n early the same length occupied by the Seine . The outer

line is made up of groups of forts , redouts , and batteries . An intermediate line of eighteen forts and several batteries - extends around the city , about four and one half miles in

rear of the outer line . T he city itself is surrounded by a

c ontinuous line of bastion fronts without outworks . To

invest the present defences , as Paris and M etz were 18 —1 m m invested in 70 7 , would require an ar y of fro 500, n 000to me .

The standing army of F rance consists of twenty corp s ,

of which nineteen are in France , and one in Algeria . The home army is territorially distributed with corps head a quartens at Lille , Amiens , Rouen , Le Mans , Orle ns , n s N antes C halons , B esancon , B ourges , Tours , Ren e , , 6 4 LAND DE FE NSE S .

- Limoges , C lermont F errand , Lyons , M arseilles , M ont B pellier, Toulouse , ordeaux , and Nancy . The railway systems of F rance are adequate for the rapid transporta tion of the corp s to the positions assigned them in the line of the defense . c d m F The great defe t of the efensive syste of rance , is that the garrisons of the numerous forts and intrenched camps will greatly diminish the strength of the field army m i and may seriously i pa r its usefulness . A defensive line n like the Rhine river , consisti g of a few strong bridge heads connected by a wide , unfordable river , is in this respect very much superior to it . VI CHAPTER .

S E A -C O A ST DE F E N S E A N D N A VA L A T T A C K .

- The purpose of sea coast defense is to protect seaports , - n avy yards , arsenals , dock yards , and coaling stations r m m a m nt m a f o bo b rd e , or fro c pture by a hostile navy ; to secure harbors of refuge and naval rendezvous for friendly n aval and merchant vessels ; and to prevent the landing of m u n c t a hostile ar y po the oas for the purpose of invasion .

I n a strategical sense , coast fortifications correspond to e n the land fortr sses ear the frontier , and form a line of n v n resistance agai st in asion , a d a base for the ofl ensive operations of the navy . Permanent coast defenses are , as n re t n a rule , orga ized only to sis aval attack and assault by sm all landing parties ; some of the important naval stations m are , however , converted into intrenched ca ps equally secure against attack by sea and by land . The number of places which must be defended is much greater on the sea coast , than upon the land frontiers . A hostile army oc u t c upies only s ch places as are on its lines of opera ion , and subjects to bombardm ent only such as are fortified and garrisoned . The hostile navy , on the contrary , is liable to enter any port where there is shipping worth destroying , whether fortified or not , and is liable to subject to bom - bardm ent or indemnity any sea coast town . On the land n s m frontiers , therefore , o ly citie of ilitary value are forti - s e m m fi ed, while on the sea coa t ev ry co ercial port is forti m a fi ed, whether it is of ilitary and n val value or not . The places to be fortified are usually determined by a s ffi e B oard or C ommittee , con isting of o c rs of both the Army B for a nd the Navy . A oard this purpose was appointed 47 C O ST D 48 A E FE NSES . by the President of the United States in 1885 in accordance B with an Act of C ongress . This oard was composed of the

Secretary of War, two ofiicers of engineers and two of rm ffi ordnance of the A y , two o cers of the Navy , and two % civilians ; its duty was to examine and report at what ports fortifications or other defenses are most urgently re k quired , the character and ind of defenses best adapted for c m m ” each , with referen e to ar a ent . The report of the B oard was submitted in 1886 ; it gave a list of twenty-seven ports on the coasts and great lakes of the United States n where fortifications were urge tly required . The estimated cost of these defenses was , 800. - N aval Vessels. Naval vessels are divided into two — rm classes armored and una ored. While all naval vessels are constructed primarily for naval combat , those of the

first class , being to a certain extent protected against c hostile artillery , are capable of atta king coast defen ses . m Unar ored vessels can attack defenseless ports only . The m m ar ored vessels of a navy are battleships , ar ored cruisers , and coast defense vessels . — - B attleship s. B attleships are sea going vessels which m carry a heavy arma ent , and have their heavy guns and engines protected by thick armor . Plate XVI shows the general characteristics of a battleship , being a diagram of the u a ship of type of the Massach setts , Indiana , and

Oregon of our own navy . The dimensions of these ships m 69 2 are , length 384 feet , bea feet , draft 7 feet , and dis p lacement about tons . Their protection against an m m direct fire lies in ar ored belt , ar ored bulkheads , an m m m u ar ored citadel or case ate , ar ored t rrets and shields , and an armored conning tower . In these ships the armor rm r t is steel . The a o bel s extend along the water line , and are 7% feet wide and 18 inches thick . As the ends of the ship are unarmored , to preserve the buoyancy of the vessel should these ends be destroyed , there is a steel p rotective deck inches thick extending below the water line from the bulkheads to the bow and to the stern . A similar deck covers the inclosure formed by the armor belts and bul k T T H IP BA LE S S . 49

e a h ds , and protects the machinery of the vessel . The arm ored citadel is above the armor belt and is protected by armor 5 inches thick . The turret emp lacements are m a de up of a fixed barbette foundation and a rotating turret . The armored barbette of the turret for the 13 inch gun s rises from the protective deck and has a thickness of 17 in ches ; the rotating armored turret has a thickness of 1 nc 5 i hes . In the turrets for the 8 inch guns , the barbette 1 is 0 inches thick , and the rotating turret 8 inches . The s hields for the 6 inch guns are 6 inc hes thick . The conning tower for the commander of the vessel is protected by 12 arm or plate inches thick . The only protection against m o rtar fire and aerial torpedoes lies in the protective and o rdin ary decks . The protection against submarine mines an d submarine torpedoes lies in the cellular construction of the hull , and the division of the ship below the water m lin e into water tight co partments . The hull is composed of two steel skins about 372 feet apart connected by longi tudinal and cross frames dividing the space into small m . n c e lls Fro the descriptio , it is evident that a battle ship is very much weaker to resist high angle fire and sub m arine attack , than it is to resist the direct fire of guns . m m m 1 The heavy ar a ent is ade up of four 3 inch , and 8 eight inch guns , in turrets , and four 6 inch rapid fire guns , behind shields ; the light armament consists of six

1 pound rapid fire guns , and four machine guns . Some of the small guns are mounted in the military tops of the m asts , where they are protected from machine and small m ’ ar s fire , by a steel barbette . In the principal battleships now under construction the heavy armament consists of 12 four inch guns , and twelve 6 inch rapid fire guns ; the m m m light ar a ent , of sixteen s all rapid fire , and two or three m achine guns . B attleships are arranged in B rassey ’s Naval Annual of

1900, in three classes , according to their offensive and de fensive value . Those of the first class are of recent con struction , and have a displacem ent of from to ‘ n Q i tons . The Orego type belongs to this cl ass . T hese 0 T D 5 C O AS E FE NSE S .

the second class are either somewhat smaller , or were h c onstructed before t e adoption of the latest designs . We

have no vessels belonging to this class . The third cl ass is composed of the oldest vessels in service and those of recent construction whose displac ement does not exceed s tons . The only ves el of this class in our navy is the s c m en Texa , whose displa e t is about tons , and whose a m m m 12 he vy ar a ent is ade up of two inch , six 6 inch , and - twenty two smaller guns . — 0 A rmored C ruisers Armored cruisers are sea-going s vessels in which protection is acrificed to secure speed. h Pl . XVIII , F ig. 1 shows t e characteristics of this cl ass of m vessels , being a diagra of the armored cruiser N e w % ork H m . er len th 380 e of our Navy di ensions are , g f et , beam dra 26 t dis lacem 65 feet , ft % fee , p ent tons . H e r pro tection a fire is m a e m r ag inst direct d up of an ar o belt ,

armored turrets , and shields . The armor belt is 4 i n ches e thick and extends the ntire length of the ship . T he p ro tective deckextends from bow to stern ; it is hori z ontal the along the axis of ship and inclined along the side s . e The horizontal part is 3 inch s , and the inclined part is 6 ar t inches thick . The b bet e of the turret emplacemen ts for 1 n es n the 8 inch guns is 0 i ch , a d the revolving turret 7

inches thick . The shields which inclose the spon son s for 4 nc s the small guns are i he thick . The protection again st is ec high angle fire the prot tive deck , and against sub r marine attack , the cellula bottom and water tight c om a m rm e p artm ents of the hull . The r or of an a or d c rui ser is intended to afford protection against the direct im pact - n of the armor pierci g , rapid fire guns . m m m six 8 The heavy ar a ent is ade up of inch guns , m two in each turret , and two ounted in broadside ; and twelve 4 inch rapid fire guns in sponsons along the sid e s ; 6 the light armament consists of eight pound , and two m uns . 1 pound , rapid fire g , and two achine guns Armored ac - s e ense cruisers could not alone att k sea coa t d f s , but as aval flee h m s they make a p art of every n t , t ey u t be con ' k \ smac . \m szdered in discussing the prebab\e n ay a

T D 5 2 C O AS E FE NSE S .

m attack against land defenses ay be first , by simpl e bom bardment to injure the armament and shelters of the m defense , and to de oralize the garrison so that it will sur render the works ; second , to silence the armament and to destroy the shelters so that the works may be taken by assault by a landing party usually disembarked under the t protection of the fleet ; third , o silence the guns and to demoralize the defenders so that obstructions m ay be re moved and the fleet allowed to steam past the wo rks to reach an objective in their rear . Attacks by simple bombardment have been very com

m on . W ar and occasionally successful In our C ivil , Fort

Henry on the Tennessee river , Forts C larke and H atteras B at Hatteras Inlet , Forts eauregard and Walker at Port r e Royal were either su rend red or abandoned , as a re sult of m m n n m . I n a bo bard e t , before a la d attack was ade 1882, E the defenses of Alexandria , gypt , were also abandoned m as a result of a bombard ent . Attack by bombardment e will not ordinarily result in the capture of coast d fe nses , if they are properly located and constructed ; the bom bard mu u m te ment st be s pple en d by a land attack . In the examples given above , except Alexandria , the comm ander of each fort was aware that a land force much supe rior to his garrison accompanied the attacking fleet ; this fact largely influenced him in surrendering or abandoning his works , before they were assaulted . The second method is the only effective way in which d good lan defenses can be attacked . The land attac k m ay m ma u d be a si ple assault , or it y be a reg lar siege , ep e nding upon the strength of the defenses on the land side . In our r F m C ivil Wa , F ort isher at the outh of the C ape Fear river was taken by assault , while Fort Wagner at the entrance of C harleston harbor , Fort Pulaski at the entrance of the S H d avannah river , the defenses of Mobile , Port u son , and u Vicksburg were taken by reg lar siege , usually after one

m . S i C a or ore assaults had been repulsed ant ago , ub , was S - m War also taken , in the panish A erican , by a land force ,

disembarked under the protection of the fleet . F R M O A F T T I E V L O O BS RUC O NS . 53

The thirdEmethod is employed in attacking cities which r a e situated on the banks of rivers or deep estuaries , where the works of defense are constructed well in advance of

the places to be protected . The success of the attack will d epend largely upon the character of the obstructions . G uns alone cannot prevent the passage of a hostile fleet , as was shown by the operations of the Union fleet on the

Mississippi river during the C ivil War, when wooden ships s J uccessfully passed Forts St . Philip and ackson near the m outh of that river , in advancing to attack New Orleans . A channel which is well obstructed by submarine mines in good condition , or other effective means , can only be used by a hostile fleet after the obstructions are wholly or m partially re oved . The removal of the obstructions is an exceedingly difficult operation and usually involves the capture of the flanking batteries or works . CHAPTER VI I .

L E E N T S O F C O A ST DE F E N E M S E .

T he various elements which make up the defense of t s m s o important seapor s are gun , ortar , t rpedoes , submarine b n e s mines , o structio s , harbor defens ves els , torpedo boats , and search lights . — m e e G uns Guns are e ploy d to p netrate the sides , and e ess occasionally the d cks of naval v els , and to com bat m e their artillery . They are ount d either in fixed batte ries ss s or in harbor defense ve el . They are divided into three - classes : heavy armor piercing guns to penetrate the belt d r t e e and n m line , bulkhea , ba be t , turr t , co ning tower ar or ; light armor-piercing rapid fire guns to penetrate the citadel a m e un m a armor , and r or d g shields ; s ll rapid fire and s ne a all arm s machine gun to pe tr te un ored parts of a ve sel , s to repel boat attack , and to protect lines of subm arine ns mines and obstructio . In our service the armor-piercing guns range from the e r c c s 8 inch to the 16 inch rifle . Th i hara teri tics are given in the following table

s ' ' h N Le W r P uo wc rl u. C H A R ls. 1

C A L13 8 3 ° Smox rzL L sx-x P o wumt I N m s

e e t es rm - The proj ctil s for h e guns are a or piercing ,

. common , and torpedo shells The light armor-piercing rapid fire guns in our servic e are the 5 inch and 6 inch rapid fire guns ; the smaller rapid 54 A N D T G UNS MO R ARS . 55

fire guns are the 6 pounder inch ), and the 15 pounder

( 3 inch ). Their characteristics are given in the following table

' ' r HA R G E Wr . P R O I E C T I LE SH O T S P E R W . C ALI B E R . C L B S M I N UT E

The penetrations of all armor-piercing gun s in wrought iron or soft steel m ay be roughly determined by using ’ C aptain Orde B rowne s rule of one caliber penetration for every thousand feet of remaining velocity . More accurate n s formulae are given in ordna ce manual . The penetration K s e e m e in Harveyized or rupp te l is v ry uch l ss . The m achine guns in our service are the Gatling and

Gardin er guns . — r d n fire M ortars . C u ve or high a gle of howitzers and em ed a ac the dec s va m ortars is ploy to tt k k of na l vessel s . In our service the 12 inch mortar is used for this purpose ; the characteristics are given in the following table :

' ' R A N G E A r wm c ' u H ARG E W r P R O I E C T I LE M uz V E L M U % . E N E RG % Q C ' C A LI B E R xv C A N P E N E T RA T E L B S I N L B % F T S E L F T T o N s AR M O R E D D E C R s

12 nc 800—1000 1 to 5 m i h iles .

— r r T orp edoes . To pedoes a e employed either to attack h e s a e s and two ds t hulls or deck of nav l v s els , are of kin , r aerial and submarine . The form er a e proj ected through r a th e ai , and the l tter are proj ected or propelled under n eath the surface of the water . r do ur s r A erial to p e es, in o ervice , a e projected from m u s are ers the 8 p neu atic g n , and of two calib , inch and T h rac th e 15 inch torpedo . e cont t specifications of the 15 inc h pneumatic guns mounted in our defenses are T o projec t a sh ell containing 50 lbs of explosive yds 1m 4 m ’5 200 500 C T 56 O AS DE FE NSE S .

At the maximum range one-third of the shots must fall in an area 360x 90feet . It is also proposed to use this u weapon in attacking the h lls of naval vessels , by explod ing the torpedoes under water , in the vicinity of the hull . Submarine torp edoes are water-tight boats containing a large charge of explosive and some form of m otor for m u propelling the underneath the s rface of the water , so

that they will strike a naval vessel below the belt armor .

They are divided into two classes , the simp le automobile

and the dirigible torp edoes. To the first class belong the W S w H th e hitehead , ch artzkopf , and owell ; to latter , the B - La rennan , Sims E dison , y , and various others . T he Whitehead tor edo p has a cigar shaped body of ste el ,

from 11 to 19 feet long , and f1 om 11 to 19 inches in

diameter . Its motive power is compressed air which

operates two twin screw propellers , and gives the torpedo 28 29 1 1 a velocity of to knots for a range of 000to 500yards . The head of the torpedo contains 100 or more pounds of u explosive , ignited by a percussion or a delayed action f se . The submergence and direction of the torpedo are regulated by vertical and horizontal rudders operated by an ingen m m ious and co plicated echanism . The torpedo must be

carefully aimed , as it is beyond the control of the operator

as soon as set in motion . The Schwartz kopf is simply a W modification of the hitehead torpedo , the case being - H phosphor bronze . The owell torp edo is similar to the W m hitehead in appearance ; it contains less echanism , m sm m m and can be ade aller , for the sa e a ount of explosiv e . The motive power is the energy stored in a fly wheel weigh

ing 130pounds , which is given a speed of revolution s

a minute by a jet of steam . The rotatory motion of the d wheel tends to keep the torpe o in its original path . The 100 m charge is or ore pounds of explosive , as in the White m in head . S all changes submergence and direction are efl ected by vertical and horizontal rudders operated by

special mechanism . These simple automobile torpedoes are intended primarily for use on naval vessels and torpedo f boats, where they are aimed by m eans o tubes T P D O R E O E S . 57

should a fleet be blockaded in a harbor , they might also be used in harbor defense . Dirigible torp edoes are automobile torpedoes which are under the control of the operator until they have com D n m pl eted their runs . uri g this ti e the torpedo may be

stopped , or the direction of the path changed ; in some torpedoes the change may be as much as There are many varieties of these torpedoes differing in their motive

powers . B rennan tor edo B The p , adopted by Great ritain , is propelled and directed by means of two strong steel wires which are wound on reels in the torpedo and are rapidly n unwound by a statio ary engine on shore . These wires unwind at high velocities smaller and finer wires which are

wound on spools attached to the two propellor shafts , and ’ thus rotate these shafts . The direction of the torpedo s p ath is changed by means of vertical rudders O perated in an ingenious way by varying the stress on the main shore m e wires . Sub ergence is secur d by horizontal rudders m operated by a special echanism . The torpedo can be ° directed in a path making an angle of 40 with its straight 200 away course . Its charge is pounds of explosive , and 20 m its velocity is iles per hour over a range of one mile . The route of the torpedo is indicated by a track of calcium phosphate which burns when it comes in contact with the

water . Sims-E dison tor edo The p is used in this country , and

is propelled by a dynamo on shore , which operates a motor inside the torpedo ; the connection between the two is a cable which is stored in the torpedo and is gradually paid m out as the torpedo oves . It is directed by means of a

vertical rudder operated by an electric current . The tor pedo is suspended at a fixed distance below the surface of the water by a float ; the float is filled with a light substance which stops the leakage through any holes formed by the ’ m assailed vessel s achine or rapid fire guns . B efore ac m ceptance by the govern ent , each torpedo is required to t sue devel op a sp eed of 18 miles an h our over a ran ge. s 8 C O ST D 5 A E FE NSE S . m to tee in ad ile , s r an arc whose r ius is 300 feet , and to s e dive at full p ed without injury under a floating spar. I ts 1 charge is 00to 200pounds of explosive . O ther dirigible torpedoes employ compressed carbonic as mm a as acid g , storage batteries , a oni cal g , or compressed T h air as their motive powers . e direction is usually given by a vertical rudder which is operated by a current of e s te electricity , carri d by in ula d wires stored in the torpedo s m - and paid out a in the Si s E dison . S m e r e a e d ub arin to pedo s are v luabl in harbor efense , as they may be used in harbors in which the channels are u are too deep , the c rrents too swift , or the tidal range is m too great for the use of sub arine mines . — Submarine M ines A subm arine mine is a case con taining a suffi cient charge of explosive to destroy the hull m m of a vessel , and so e for of detonator for exploding the ffe the charge . Since the e ct of charge varies with its ex its m r plo sive force , a ount , and inve sely as the square of the distance it is e ssential to use a high power explosive , , a large charge , and to explode the mine as close as pos sible to the hull of the vessel . The available explosives in the order of their app roxi

‘ mate strength are as follows

E x os e G e atine 100 e at e st n pl iv l , r l iv re gth . N 1 D nam te o . 80 y i , n 80 G uncotto , n G n der 30 F i e u pow ,

S m m es are ss and ub arine in cla ed as buoyant ground . A buoyant mine is one which floats underneath the surface e e of the water , between the l v l of the armor belt and the s es keel of the naval ve sel to be d troyed . It is held in place by an anchor so that the explosion may take place in c on ’ tact with the ship s hull . The case must be strong enough to stand the shocks of friendly vessels and have sufficient u e buoyancy to s pport its charg , the anchoring , and electric s n m cable . The latter conditio li its its use to water not over n T he m o e hundred feet deep . ine must not be greatly de pressed by the action of the current ; this condition limits

60 C O T D AS E FE NSE S .

r form of batte y , the other pole being connected with the B m earth . y si ply closing the key , the operator can de m tonate the fuse and explode the ine . This arrangement P 1 2 is shown in . XVIII , Fig . , in which E represents an

earth plate at one end of the circuit , and the mine case at B e the other . F is the firing batt ry , K is the circuit m r closing key , and F the fuse in the sub a ine mine . I n ff order that the mine be e ective , the operator must close the key at the exact instant in which the vessel is in the

destructive radius of the mine . This involves an exact m h knowledge of the location of the ine , whic may be swinging about its anchorage due to the force of a variable

tidal current , and an exact knowledge of the location of the

vessel at each instant . It is rarely possible for the operator to locate both mine and vessel so accurately that the simple

judgment mine will be effective . Judgment mines are of

no value in a fog , or in a heavy rain storm . The contact mine is arranged in the same manner as the judgment mine except that an automatic circuit closer a m e is placed either in the buoy nt in , or in a buoy floating

over the ground mine . It is closed by the shock of the

striking vessel . To insure the explosion of the mine at the e r e s proper instant , the op rato ke p the shore key closed. When the enemy is not in the vicinity he m ay render the r s ‘ mine inope ative , by keeping the hore key open . This

i . . arrangement s shown in Pl XVIII , Fig 3, in which the is mm circuit closer represented as a ha er , formed of a thin m vertical steel rod with a heavy etallic head , which is in m s m closed in the etallic cylinder of the ubmarine ine . T he shock of a striking vessel closes the circuit by bringing the mm he d head of the ha er into contact with t si es of the case . m T he simple contact ine cannot be fired by judgm ent , nor

can it be tested for continuity of circuit . The regulated mine is arranged similarly to the contact is mine , but connected with a weak battery and an annun W m 1 c iator board . hen the ine is st uck , its number is r inform ed that v d opp ed, and the op erator is at onc e a essel

' '

1s in th e m it be a h osth e v essek h e. c an . m e field . I f MINE S . 6 1 switch into the circuit the firing battery which will detonate th e fuse and explode the mine ; or if he desires , he can ar ran ge the switches so that the firing battery is switched into the circuit automatically , by the dropping of the corresponding number on the annunciator board . The mine is n ow arranged so that it is always on guard , but is dan ge rons to the enemy alone . To insure the continuity of the m c on ductor , a fine wire shunt ay be made between the c on ductor and the metallic case , so that a break in the con duc tor may be at once detected by a galvanometer . This P arrangement is shown in I . XVIII , Fig . 3 in which SB is the signal battery , AR the annunciator , and R a high resistance coil which completes the circuit of the signal battery . A shunt circuit is also arranged so that the mine d m m m ay be fired by ju g ent ; this is o itted in the figure . - i A self acting mine s a mechanical , chemical , or electric mine , in which the entire detonating apparatus is in the mine . It explodes whenever it is struck by a vessel and is

equally dangerous to friend and foe . If all the mines of an extended field had separate shore m - conductors , the botto of the channel would be a net work of cables which would render the task of repairing any one m cable , almost hopeless . The ain shore connection for a m ti l cabl or group is , therefore , a ul p e e, a cable containing s a number of eparate insulated strands usually seven . The multiple cable runs from the operating room on shore - to a grand junction box , where each strand is joined to a m a single cable . E ach single cable y in turn run to another - junction box , where it is joined to single cables running

to several mines . Where several mines are connected - fi with the same conductor , a cut o is arranged so that the explosion of any mine cuts its connection in the junction

box , and prevents the leakage which would otherwise occur . The entire system of mines attached to the same multiple cable is called a grand group ; the system attached to the s m m r separate strand of a ultiple cable is called a ino group . ff m u are se arat from each The di erent ines of a gro p p ed.

' oth er b such a dis \ s\on or am ems. y tance, that th e exp o ; T 6 2 C O AS DE FE NSE S .

' a mine will not injure the c ase , anchor ge , or the electrical connections of its neighbors ; for mines containing one h s a 1 hundred pounds of explosive , t i is bout 00 feet . T he r m es s arrangem ent of a grand g oup of in is hown in P I . 4 e m XVIII , Fig . , in which A is th ultiple cable , B the n- m - grand junctio box , C O the inor junction boxes , and M M T the separate mines, % hen a number of contact m ines are

strung along a single conductor cable , each is called a

skirmish mine .

i m c a The op erat ng roo on shore , whi h cont ins the firing er battery , the signal batt y , the annunciators and switches , d is placed in an unexpose position , and is m ade p roof i n c w against naval fire . It s co ne ted ith the channel by a m tunnel in which are laid the ultiple cables . The weakness of any mine system lies in the injuries n caused by passi g friendly vessels , and the leakage from defective insulation ; these m ay render the mines inO p era r me tive at the c itic al mo nt . Submarine mine fields must be swept by the fire of rapid fire and m achine guns which will prevent the rem o val m a a m h m es the e . of t e in by en y In the tt ck of a ine field, es r rm s e a fleet m ay r o t to counte ining , weeping , or cr eping . x n o C ountermining con sists in e plodi g, al ng the channel e es whic h is to be op ened , l arg charg of explosive to break

es nc e . the mines , in sulated cabl or a horag s These charges m ay be in the form of aerial torpedoes ; or subm arine and e o ed the a c and mines, plac ed xpl d by l un hes torp edo in c s sts r boats of the fleet . Sweep g on i in dragging ove the

mine field a long cable attached to two boats . When an r anc hor cable is encounte ed, it is destroyed by a sm all c harge of explosive ; the mine floats to the surface and its red C r in c n shore connection is seve . eep g o sists in dragging ea the s hooks along the bottom n r hore , so as to find and destroy the m ain electric c ables connecting the torpedo m n . f system with the operati g roo At night and in a og, patrol boats must be employed to give warning of the ’ es m approach of an enemy s boat parti . The ine circuits in nn s s o th a m ay be also c onnected with th e fl ank g g t . n B T T O S RUC IO NS . 63

m any ine is interfered with , its vicinity will be swept by the fire of the guns . — O bstructions . Obstructions are any passive obstacles

which prevent a hostile fleet from using a channel , until

they are removed . Like submarine mines they must be n fl at u der the guns of the batteries . They may be either o in g or fixed . Floating obstructions are chains and cables su m pported by boom s , rafts , etc . , which extend fro shore

to shore ; they are used in closing narrow channels . They are i objectionable , as they are liable to be carried off n fl oods , and they limit the moveme nts of friendly naval and m n erchant vessels . The floating obstructio , which was c onstructed by the C onfederates across the Mississippi be l w o New Orleans , parted , during a flood , just before the

arrival of the Union fleet under Admiral Farragut . Fixed

o bstructions are cribs, piles , sunken barges , submerged

tc . . dikes , e , which wholly , or partially , close a channel T hey were extensively used in our C ivil War as they are m v ery difficult to re ove . When an active defense is to be m m ade , gaps ust be left for the passage of friendly vessels ; these may be in water too shoal for the passage of war ma v essels , or they y be under a heavy concentrated fire of

the shore batteries . The entrance to Spezia harbor in m m Italy , is partially closed , in a per anent anner , by a sub m e rged dike ; the gaps are near the shore and under the

c lose fire of heavy turret g uns . Harbor defense vessels are similar to coast defense t v essels , but s ill further sacrifice speed and seaworthiness m m to secure a heavy ar a ent , well protected by armor . m T hey are e ployed in harbors , where land batteries com bined with submarine mines cannot efi ectually close the

entrance . A harbor with a very wide entrance , or with a

very deep channel , would require harbor defense vessels

to replace coast batteries or submarine mines . T orp edo boats arm ed with simple automobile or spar

torpedoes assist the coast defense vessels . A sp ar torp edo

' e tor edo h w xeh xo eexs is a larg p s ell , attached to a sp ar h n x

Sufi ) from th e bow of a l a nc is so arran gee. u h or tug, and. T 64 C O AS DE FE NSE S .

it explodes on contac t with an obstacle . The spar is so fixed that the torpedo is exploded in contact with the hull

of a battleship , below the belt armor . Search lights enable the defenders to watch the m ove

ments of the fleet at night , and detect any attem pts to de u m r m to n an as ul stroy the s b a ine ines , or la d parties for sa t . ts ma ac in tur These ligh y be pl ed disappearing rets , as in di land defenses , or on sappearing mountings behind a ma parapet . The lights y also be placed on carriage s so as

to be moved from point to point . CHAPTER VIII .

T UR R E 'I ‘ S ( ‘ A S E M A T E S A N D B A R B E T T E B A T , T E R IE S .

The heavy armor-p iercing guns of coast batteries are m e m ounted in turr ts , case ates , or in barbette batteries . T r — u rets . The turret mounting has the advantage of - - all round fire , and all round protection for the gun and its e m d tach ent ; the chase of the gun alone is exposed to fire . i The pr ncipal objection to it is its cost , which limits its use to low contracted sites where practically all-round fire and p rotection are deemed essential ; an additional objection is

its contracted interior space . There are two general types

of turrets , the cylindrical and the spherical ; the former a m m m y be ade of wrought iron , co pound amor , or steel ;

th e latter is made of chilled cast iron . Wrought iron tur t m D re s are e ployed in the defenses of over in E ngland , St . B P etersburg in Russia , Antwerp in elgium , and C allao in P D ma eru . The over turret , which y be taken as a type , is a cylinder whose interior diameter is 32 feet and interior m h eight 9 feet . The sides are ade of three layers of 7 inch wrought iron plates , separated by two layers of 2 inch p lates . The total thickness is , therefore , 25 inches . The to 16 tal weight of the turret with its two inch , 80 ton , - fl m uzzle loading , ri es is about tons , which is borne by a ring of steel rollers . The turret and guns are operated 200 - m b . di y a horse power stea engine The loa ng rooms , m agazines , etc are in the pier upon which the turret is c onstructed . C ylindrical turrets would now be m ade of steel , which has replaced wrought iron in armor construc tion . The requisite thickness would be determined by the table of penetrations of the most powerfni gnn sh oes . 66 C O A ST D E F E N S E .

T he chilled cast-iron turrets are m ade by the Gruson T he are of the w l -k w C ompany of G erm any . y e l no n m ush ar m ade of ar b oc s of m w room form , and e l ge l k etal hich v s support eac h other as the ousso irs of a dome . Thi ob viates the nec essity of us ing bolts whic h are elem ents of weakness in cylindrical turrets ; the voussoirs are held in place by steel keys whic h are ins erted in grooves in their Th use steam we is av ed as far as os sides . e of po r oid p sible , and in those rec ently designed for gun s all 11 inc h caliber tur e s and u s are m a e vr t or less, the r t g n n u ed en irely by - w r b mea ra l c ac c m l man po er, o y ns of hyd u i u u ato rs fil led r et fo w 11 c by hand pump s . A tu r r t o in h guns requires a me c sis t oflic er and f rt - detac h nt on ing of one , o y one m en . 4 t e te r am ete w This turret is 3 % fee x ior di r , and ith its sub ru t e of a e and a s is ea 20 eet hi st c ur iron pl t s ngle , n rly f gh . l r ts a e s w Like the sma le turre for l nd d fen e , the eight of the r a i i al ste turret is bo ne by r ng of con c el rollers . T he weight resting on these rollers is 827 long tons ; in addition we to this the glac is armor ighs 460 tons . The re sisting tur et is timat as t-to power of the r es ed foo ns , or about the striking energy of a 12 inc h gun fired at a ran ge r e s use h of yards . These tu r t are d in t e coast defenses s s m H of E urope , on the coa t of Ger any , olland , Austria , d in Janeiro B and Italy , an the defenses of Rio , razil . — ac C asemates . I f the front of att k be limited, the case mate mounting has the advantage over the barbette m oun t ing of thoroughly protecting the guns and detachme nts ’ from the enemy s fire and of allowing the guns to be sp ac ed with intervals of 30 feet ; it has the advantage over the

m c . I t has d e s turret , of giving ore interior spa e the ef ct of fir mi a narrow field of view and e , usually li ted to a sec tor m n m of 70degrees ; and , if of ar or , of costi g nearly as uc h c per gun as a two gun turret . These defe ts tend to limit t mm its use to low , contracted si es , which co and narrow B a n Sta channels . In Great rit i and the United tes , the casemate has been wholly replac ed in the new coast defense

e te m n . p lans, by barb t ou tings th B efore the invention of rifl ed artxh ew s e N omad

T 68 C O AS DE FE NSE S .

plates were connected by bolts , which fastened the inter mediate plate to each of the others . The shields used in closing the casemates were made of single plates each 8 x 12 feet ; the continuous scarps were made in the same manner m of smaller plates or p lanks . So e of the barbette batteries were also converted into casemates , by erecting a shield between two traverses , and covering the emplacem ents r - with a tempora y , or permanent , splinter proof roof . In 1870 the Gruson C ompany began the construction m - of casemates co posed wholly of chilled cast iron . This

m n P I . case ate , as at present constructed , is show in XIX , 2 Figs . 1 and . Fig . 1 is a vertical section and elevation of m 2 the casemate through the e brasure ; Fig . is a horizontal

section and plan of the chilled iron face , also through the m embrasure . So e of the advantages over other typ es

claimed for the chilled iron casemate are , the surface s ex posed to fire are double curved surfaces ; no bolts are necessary in its construction ; and the shock is transm itted

to a large area of structure by the voussoir construction . These casemates are found in the coast defenses of G er m H l d B m any , Austria , o lan , elgiu , and Italy . At the m W m m n outh of the eser , is an ar ored case ate for nine gu s , - surmounted by three two gun turrets . In France som e of the old masonry works have been strengthened by inc reas ing the thickness of the scarp walls by an exterior wall of 25 m concrete , or ore feet thick . This makes the gun a ports very l rge and deep , which is objectionable . t B at r — B arbet e te ies . The barbette mounting being the m most econo ical , is the one generally adopted for - sea coast guns . If the gun be mounted on a center pintle carriage it may have an all-round fire like the turret ; if

on a front pintle carriage , the flank guns of a battery 1 sweep over a sector of 70 degrees , and the interior guns 14 over a sector of 0 degrees . If the site be an elevated m one , the simple barbette ounting gives the gun all nec es r a the l sa y protection against n val fire ; and if site be ow, the disappearing mounting gives the additional protection ‘ r i ments m a h e eh nost as snie equred. The gun detach y h B A R B T ’I ‘ T T I E E BA E R E S . 69 screened from shell fragments and shrapnel as those in turrets and casemates , by the use of vertical or horizontal shields attached to the gun carriages . An objection to the barbette mounting is the great horizontal development of r the batte y , which prevents its use in very contracted sites . m m m The si ple barbette ounting is the ost economical , and in our defenses costs , including emplacement , gun , and a i c rr age , about for the 8 inch gun , for the 10 1 inch gun , and for the 2 inch gun . A vertical shield may be added for the protection of the gun detach m ent while loading and pointing the gun . In elevated sites the simple barbette offers a difficult target to naval fi re a o . At Santiago , C uba , the Morro and S c pa batteries w 2 ere on opposite sides of the entrance , on bluffs 00 feet h igh ; on June 6th , 1898 , these batteries were attacked by w 1 t elve naval vessels and auxiliary cruisers , mounting 1 2 guns of 4 inch caliber or above , and a large number of m s aller rapid fire guns . Although the bombardment was kept up for three hours , not a single gun of the 12 mounted in the defenses was injured ; as the batteries were not pro i - v ded with bomb proofs 3 men were killed and 51 wounded . - M ost of the shore guns being old muzzle loaders , were unable to do any execution at the range of the ships and n s oon ceased firi g ; the fire of the attack was , therefore , delivered under the most favorable conditions .

In low sites , though the guns are not easily hit , the fire of the simple barbette battery can ordinarily be silenced , if the fleet has a much stronger armament . This was well illustrated in the attack on Forts Walker and B eauregard at C War Port Royal in our ivil , where the gunners were compelled to abandon their guns under a heavy fire from a fleet of wooden vessels ; and in the attacks on the inner lines of Alexandria , where the guns were not injured but m the gunners were co pelled to abandon them . In low sites , therefore , the guns should be mounted on disappear ing mountings . — Disapp earing M ountings. There are two general types

'

i f ch h exn \.n of disapp ear ng mountings, the object o ea g C T D 7O O AS E FE NSE S . lower the gun during the proc ess of loading so that it will n not be exposed to fire . In our service the gu , in its load ing position , lies below the trajectory of a shot grazing the interior crest with a fall of This is about the angle of e fall of a 12 inch projectile fir d at a range of yards . n- h the i One type is the gu lift, in w ich gun s placed on a platform which is raised and lowered by powerful m a m chinery . Only a few guns are thus ounted as the cost of - the gun lift has been found to be very great . T he other arin un-carria h type is the disapp e g g ge, wit or without counterweights ; in this the gun alone is lowered , by rotat ing the axis of the trunnions about an axis below the - m level of the parapet . In the hydro pneu atic carriage , used in the B ritish service , there is a horizontal steel shield just below the level of the parapet for the protec tion of the n m m men gu detach ent fro frag ts of shell and shrapnel .

The gun is elevated through a slot in the shield , which is also closed by an iron door if the gun is exposed to all round fire ; in this type hydraulic machinery is necessary for maneuvering the gun . In our service all guns are - maneuvred by man power , and the horizontal shield is s omitted . A compared with the simple barbette carriages the disappearing mountings are more expensive and more m m co plicated ; they are thus ore liable to get out of order . m m m If stea or si ilar power is e ployed to raise the gun, this adds both to the expense and to the complexity of its m . n n parts In our defenses the disappearing ou ti g costs , m including emplace ent , gun , and carriage , about for the 8 inch ; for the 10inch ; and for the

12 inch gun . The required thickness of the parapet in front of a m 40 barbette is given by ost authorities as feet of sand , or its equivalent in concrete ; in our service one foot of con crete is considered equal to two of sand . In the concrete are imbedded large irregular stones to deflect the p roj ec of tiles . This thickness parapet is based upon the results of the bombardment of Alexandria where a sand parapet 25 m 1 feet thick resisted the shots fired fro the 6 inch , 80 T T T T I I BARBE E BA E R E S . 7

- ton , muzzle loading gun . In our new works , the parapets for heavy armor-piercing guns consist of a wall of concrete

15 feet thick , in front of which is a parapet of sand 20feet thick . This is thicker than is necessary to resist simple penetration and would probably afford a serviceable cover were the earth covering largely displaced by torpedo shells . The triangular profile is the best form of parapet l ff ffi for al barbette batteries , as it o ers a di cult target to direct fire . The upper part of the parapet , to a point 7 m m t fe et beyond the uzzle of the gun , ust be a hick bed of c oncrete to withstand the blast of the gun .

In a barbette battery , guns are usually placed at inter v als of 100 to 125 feet ; they are separated by traverses n r which contain the magazines , loadi g oom s, etc . In the new works , the magazines are protected from direct fire by at le ast 30feet of concrete or its equivalent , and from vertical 10 fire , by a concrete roof at least feet thick ; the roof is m ade flat and is supported by I beams . In hastily con structed batteries , the roof may be made of one or more layers of railway rails placed in close contact , and covered m with planks or bea s to support an earth covering . As

e d m . the m agazin s , loa ing roo s , etc , are usually below , and n m at some dista ce fro the loading platform , ammunition

hoists or lifts , and overhead railways are provided for the m n movement of a mu ition . Pl . XIX , Figs . 3 and 4 show the section and plan of an emplacement for a barbette gun

on a disappearing carriage . 4 B In the plan , Fig . , the broken line C is the interior D i crest, and the line E s the exterior line of the concrete wall which protects the gun emplacement and magazine ; e the earth parap t is a continuation of this concrete wall . At V is a small recess which is used as an observation r station . The te rep lein lies between the interior crest and the broken line F G ; it is terminated in rear of the g un emplacement by a parade wall and on either side by ram part slopes which terminate at the parade in the lines HI - e and KL . The gun pit at A is sunk b low the level of the

terreplein , and so constructed as to give the gun a horizontal 7 2 C O AST DE FE NSE S .

1 sector of fire of 40 degrees . The floors of the magazine - m M and the other bomb proof cha bers , N , O , P , Q , R , and e S are on the l vel of the parade , so as to allow the necos m - sary thickness of overhead cover . A bo b proof passage leads from the magazine to the parade , which with iron - doors in the parade wall , gives access to the bomb proofs. A stairway to the left of the gun emplacement and another near the observation station connect the terreplein with the parade . The rap id fire guns m ay be mounted as in land de f ns s in e e , in turrets , or barbette batteries . If in the latter, they are similar to the batteries for heavy armor-piercing guns ; the thickness of the parapet , and overhead cover r l for magazines are however g eat y reduced , as these bat teries would probably be exposed only to the fire of similar guns afloat . Gun batteries should not be located in front m al l of , or close to , asonry w ls or rocky s opes , whose frag n ments may be throw into the batteries . A parados in is rear of the guns objectionable , as fragments of shells exploding in its face are thrown back sixty or more yards. B atteries for howitz ers and mortars are easily protected from direct and shrapnel fire by parapets similar to those n m for gu s , or by placing the in natural depressions . I n our service , the mortar batteries are arranged in pits each containing four mortars . The pits are separated by tra verses containing the magazines , and may be placed in in line , in echelon , or a square of four pits , depending upon the conformation of the ground . The line and echelon arrangements have the advantage of leaving the pits O pen le n the e to the rear , and thus sse ing chances of injury to th l n e t t. me , by fragments of sh l s which just graze he parape I CHAPTER X .

R R A N G E E N T O F ( TO A ST D E F E N S E W A M O R K S .

— C aliber of G uns T he greatest caliber of the guns in the coast defense works of any position depends upon the C lass of vessels which will probably be engaged in the at be s ffi m tack . I f the position of u cient i portance to warrant ’ em a serious attack by the en y s fleet , som e of the g uns u ea e st should be eq al at l st to the h avie guns afloat , so that no part of any naval vessel would be proof against their 12 fire . T he inch gun fulfils this condition . As a certain moral advantage is always secured by having som e guns a e h little more pow rful than those of t e fleet , heavier guns than any afloat are sometimes mounted in important posi ] tions . For the artillery due , the relative proportion of m - n - the heavy ar or pierci g , the light armor piercing , and the sm aller rapid fire guns should be approximately the the - sam e as on a battleship . All heavy armor piercing ne not m m m guns ed be of the axi u caliber , as the heaviest arm or is confined to a small portion of a battleship ; on the 1 other parts of the sh p , the smaller caliber guns are almost

equally effective , are less expensive , and can be fired more

r . apidly As battleships will not ordinarily operate singly ,

as long as there is an opposing navy , l ess important har bors need only be defended by guns of the caliber of the m armored cruisers , or unar ored vessels . The largest g uns i 10 n the first type of vessels are the inch guns , and in the

second , the 6 inch rapid fire guns . un — N umber of G s . The number of guns in the coast i nd batteries of any posit on will depe upon its importance , t he hydrography of the field of attack , and the kind of C O T D E N 74 AS R E SE S .

e s mounting nec s ary for each class of guns . The imp ortance m of the position fro a naval , military , commercial , and

political point of view , will determine both the nature of

the attack , and the amount of money which the civil and m l ilitary authorities are wil ing to allot for its protection . The hydrograp hy of the field of attackwill determine the

number of vessels and the g uns , which can be utilized by

. e ta the assailant If this fi ld of at ck be an open one , the d water not too eep , nor the current too strong , every vessel m n n e ay be a chored in li e , so as to utiliz all the guns of a m t s broadside si ul aneou ly . If the field of fire be narrow

and the current swift , the vessels are compelled to advance m e l in colu n , and if the channel b obstructed , on y a few e guns of the fle t can be utilized . T he kind of mounting will determine the number of guns which can be put in position for any given sum of money ; this varies from 12 u for a single inch g n in barbette , to for n 12 - a si gle inch gun in a two gun turret . No general rules can be given for the number of guns in coast defense works ; the number can only be determined by a study of local conditions . — Line of Defense I f the object of the batteries be to n m m preve t the destruction of a place by bo bard ent , the

artillery line should, if possible , be located about six miles in front of the position to be protected. This will compel e e the hostile fleet to silenc the batt ries , before it can bom

bard the port which is covered by them . This condition l can , however , be fulfill ed on y in the defense of ports which lie in deep , narrow estuaries , or near the mouths of navi gable rivers . When this condition cannot be fulfilled the artillery line should be constructed as far in advance of the position as the topography of the site will permit . Since

all the guns of the attack , both heavy and light , are prac l m tically in the same ine , the sa e disposition should be m e - t the ade of the count r ba tering guns of line of defense . This will prevent the fleet from conc entrating its fire first n e n n on the advanced gu s of the d fe se , a d then on the re tired n i one if th e were estahh shed in o es, as m ght be d y

T D E N 76 C O AS E E SE S .

r n r m c h e m r be fired , orthe a ge f o whi th y ust be fi ed to hit the r h l m e a dec re e the ff r batte y . T is wil at ri lly as e ect of its fi e, r tta th as was illust ated in the a ck of e batteries of Santiago, r C uba ; this is the p incipal advantage of an elevated site. An increase in the elevation of a battery al so decreases the ’ h c angle of fall of t e ship s proje tiles , and thus increases ff b th r n e e e . the p otectio o red y parap t This effect is small , as an increase of elevation of 50feet for every 1000yards of ec e r e r n range , is n ssa y to d c ease the angle of fall o e degree. The only objection to an elevated site is the dead space which is formed in front of the guns ; the width of this m e u the space is approxi ately q al to elevation of the gun, multiplied by the natural cotangent of the angle of m axi

mum depression of the gun . When the defense of this m c in space is of i portan e , as the defense of a narrow chan l m ne , the advantages of the elevated site ust be sacrificed , c m be t or the dead spa e ust swep by additional batteries.

. - F ir h High angle e . At t e proving grounds of the m n 189 1 Krupp works, G er a y , in 0, at the range of 387 yards, 2 e the 9 c . m . howitz r was fired at a horizontal steel deck 1 T he m 17%x4/2 yards . deck was ade of three 1 inch plates, and one inch plate riveted together and supported by m W 45 I bea s . ith an angle of elevation of degrees , the

target was struck by the tenth shot , which penetrated the

target and the earth beneath . With an elevation of 60 h e was degrees, t e targ t struck and penetrated by the six i 1 teenth shot . At Tokio , Japan , n 891 , a similar target n 20x6 yards , and 3 i ches thick was hit and penetrated by - three shots out of forty five, fired at an angle of elevation ee e 3554 s m 2 of 60degr s , at a rang of yard , fro the 8 c . m . howitzer ; and by four shots out of seventy-three from the H d e e 2 m m . a 4 . c . ortar the targ t be n of the size of a ship , u h r 20% of the shots would have str ck e deck . General Abbot deduces the following formula for the number of

shots which would strike a ship , if fired from a mortar battery of sixteen mortars arranged in four symmetrically 1 n hi X _ spaced pits as desig ed by m ; , in which R £21

z = the X R . p ercentage of hits , and range in yards The T T C O AS BAT E RI E S . 77

ship is assumed to lie at the center of impact . From the e xperiments given and from a study of the con struction of

naval vessels , it is evident that howitzers and mortars for high angle fire are very valuable elements of any system m m n of coast defenses . In the ar a e t for our coast defenses , % B on r fic i n ” recommended by the oard F o ti at o s, the ratio of the number of mortars to that of armor-piercing guns

was approximately seven sixths . High-angle fire is especially valuable to prevent a fleet

from lying at anchor to bombard a city , or from taking

refuge in an achorage during a storm . — R ange and P osition F inders Range and position finders are provided for each battery to determine the dis m n tance and direction of the target fro the observi g station , and a relocating apparatus is essential for transferring the origin of coOrdinates from the observation station to

the directing gun of each battery , The relocating room is

connected electrically with the observation station . — F ire C ontrol . The united action of the batteries is

secured , by connecting the station of the commander of t mm he defenses with that of each battery co ander , by means of electric circuits for communicating orders and

information ; all wires are placed underground . — i L P arties Defense A ga nst and . To defeat an attack m by landing parties , auxiliary rapid fire and achine gun batteries are attached to the batteries of large guns ; these m ay be mounted in disappearing turrets or in open batter

ies . To check an assault , each battery should be inclosed

by a strong obstacle , such as a high wire entanglement in T a shallow ditch . he flanks of a position should be guarded

by strong permanent or field works . A battery in an

isolated position , where it can receive little aid from the

other land batteries , should be enclosed m a permanent - redout or fort of strong profile , with ample bomb proofs

for the garrison and supplies . — O bstructions The obstructions are generally placed

on the same general line as the batteries , but local con diti n in e ne m as o s m ay make it advisabl e to piace th em , 8 C O T 7 AS DE FE NSE S .

or in the rear of this line . The submarine mine field is

usually of considerable width , and is made up of a number

of grand groups of regulated mines , in advance of which m m are a nu ber of contact , or skir ish mines attached to a

single cable . Auxiliary channels may be closed, during n - the continua ce of war , by self acting mines . The mine h r m h field is swept by t e fi e of ac ine and rapid fire guns. E m — H m sca p le. a pton Roads ( Pl . XX ), at the mouth of J me r - r the a s Rive , Virginia , is the best land locked ancho n a he age o the Atlantic C o st , south of New %ork , and is t a - r nd g teway to the navy yard and coaling po t of Norfolk , a - n w Vir to the ship yards a d coaling port at Ne port News , t ginia . Unless the entrance to the roads be properly for i fie l m s s ro d, a hosti e fleet ay take po ses ion of it to dest y its - - n shipping , the navy yard , the ship yards , and the coali g e stations which are reached from it , and use this achorag

as a temporary base . % The B oard on F ortifications and Other Defenses recomm ended for its defense the following : 4 16 nc uns 2 2- un tu ets 2 o e in ooms i h g , g rr , p rat g r ,

10 12 nc uns 10 c ase m ate s 8 e e t c ts i h g , , l c ri ligh , 20 10 nc uns 20 disa ea n un c a ia es i h g , pp ri gg rr g , 16 12 nc m o s 400 su m a ne m nes i h rtar , b ri i . The problem of defense which it is proposed to use as is an illustration of the principles, is to determine the d position of these elements to pre vent the entrance of the

ho stile fleet . — to Hydrograp hy . North of the entrance [P] . XIX] s n n Hampton Roads i a low peni sula of sand , lying betwee C hesapeake B ay and Mill C reek ; the latter is an extensive s shallow tidal basin . The lower end of the peninsula i n n occupied by Fort Monroe , a pe tagonal m asonry bastio e fort of the old typ , which has a tier of casemates and r mu - a tier of ba bettes , for old zzle loading guns . Above t n Fort Monroe , for a dis a ce of a mile , the peninsula rises n e a e o ly a few fe t bove the wat r ; beyond that , is a ridge e of sand dunes rising to a h ight of about twenty feet . outh he n an her lon e S of t e trance is ot g p ninsula , Willough ‘ b Sands it c is al so term in at ed at th e sh ore en n ox y p , whi h j D F H P T O E FE NSE O AM N RO ADS . 79

a ridge of sand dunes rising to a height of about forty f e et. B t ehind h e dunes is low cultivated ground . The m ain ship channel which enters C hesapeake B ay between C a H pes C harles and enry , becomes very much contracted n e ar Thimble Shoal Light ; between this light and Hampton R oa ds its width is only about one mile . Its depth varies b etween 30 and 85 feet and the tidal current is moderately S w ift . This channel is limited on the north by Horseshoe S ho nd al , a on the south by Willoughby Shoal . At the W estern extremity of the latter is an artificial island made O f - W . rip rap , which is the site of Fort ool This is a work O f the old type and was originally designed for three tiers O f casemates , and a tier of barbettes ; only the lower tier O f m m . case ates has been co pleted An auxiliary channel , 1 6 feet deep , passes in rear of the fort . — L ine of Defense Since there is no city to protect from b m m m o bard ent , the proble is to locate the guns and oh structions so that a fleet cannot steam past the works or successfully attack them . If a line be drawn parallel to the coast and about two miles from it , the deep water area inc losed by the line will be the principal field of attack ; beyond this line , the fire of the fleet would be too inac c urate to hope to destroy or to dismount the guns of the defense . The deep water area is that in which the mini m um depth is greater than the minimum draft of a battle ship ; in attacking the batteries at the entrance of Hampton m Roads a battleship must keep in the ain ship channel .

To obtain a concentrated fire upon this field , the line of defense should , if possible , begin at some point north of

Fort Monroe , thence extend along the northern peninsula , W W across the channel at Fort ool , and along illoughby

Sandspit . The latter , however , is too far from the channel m to be a good site for guns , so all the guns ust be mounted d n W an . in Fort ool , along the Fort Mo roe peninsula A good site for the two turrets is found either at Old Point

L W . C omfort ight , or at Fort ool As the greater part of the artillery line is along the peninsula of Fort Monroe , the

on.% s e\ turrets for the 16 inch guns should be piacedin E , 80 C O AST DE FE NSE S .

and mounted on a line coinciding generally with the axis

of Willoughby Shoal . The one to the rear might be ele va ted above the advanced one , so that it could fire over it .

The best position for the casemate , assumed to be an iron L one , is near Old Point C omfort ight . Since the guns must

sweep a sector of over 100 degrees , extending from Fort W to m S L m te ool a point beyond Thi ble hoal ight , the case a for the 12 inch guns should be made slightly curved so that the extreme guns can reach the limits of the zone . The 10 inch guns would be distributed in batteries of from two to four guns , along the Fort Monroe peninsula north of the fort ; as the site is low, they should be placed on disap pearing carriages . Since the effective range of the 12 inch mortars lies between 1 and 5 miles , the two batteries of eight mortars each would be placed on the flanks of the B defense , one at A , and the other at , where they could reach vessels in and beyond the field of attack . Rapid fire guns , woul d be distributed along the line to protect the barbette guns from the rapid fire guns of the ships , and to protect the batteries from landing parties . All the batter ies in the Fort Monroe peninsula should be protected against night assaults by wire entanglements or other ob tructions m n s defended by infantry and achi e guns . The best location of the submarine mine field is between W m Forts ool and Monroe , the operating roo s being in these forts . The channel being about a mile wide , it would l be entirely c osed by two grand groups in line . The regu lated mine could be arranged in four lines distant from each other about five hundred feet . This would require

336 mines , the others might be arranged as contact mines in skirmish lines in advance of the main lines , and in the auxiliary channel in rear of Fort Wool . The electric lights would be distributed along the line . In the attack of the defenses at the entrance of Hampton Roads a fleet would be at a great disadvantage in being compelled to attack in m m a n arrow channel . The ar a ent of the defenses could no doubt be safely reduced and it is believed this has been done in the revised projects for this position . I N D E X .

F A G E

A cc e sso ry de fe nse A dvanc ed works A rm ie s A rm o red c ruisers forts

A e mode n rtill ry , r

A ttac k, E ffect of m e ans o f

B arbe tte batte rie s B a rrie r forts B astio n trace B attleships

C am s int enc ed p , r h

e n es o t ca and c omme cia C tr , p li i l r l C oast de fe nse guns

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

C u se s a m o ed r i r , r r C unett e

D nse accesso e fe , ry against l and partie s lines of de fe nse of P aris

sea-coast

work s for ne ar and distant Disappe aring m ountings

Ditc h

E ffec t of elevation . m eans of attac k E lectric al mi ne s to rpedoes E nc ein te - H igh angle fire .

I o in t i a wo k 18 70—80 nteri r l e yp c l r , Interio r wo rks Intre nc h ed camps

N aval ve ssel s

I N DE X .

ess s oast de nse V el , c fe

W o s ad anced rk , v

near and distant defense — trace o f 1870-80