r- ) I j • l/ine Warfare J NOTES I Navy Department OFFICE OF THE CHIEF OF NAVAL OPERATIONS WASHINGTON Mine Warfare
MINE WARFARE NOTES 15 July 1945 J NOTES
OpNav 30-3M-A, No. 5-45 MINING LETTER OF PROMULGATION Radar Minelaying...... 2 1. For the purpose of keeping naval personnel charged Manila Minelaying Operation...... 7 with responsibility of mine warfare continuously in British, Mine "Warfare...... 0 formed of new developments and other pertinent infor Offensive Minelaying in the Pacific War...... 14 mation relating to their field, MINE WARFARE NOTES will be issued periodically. ENEMY ACTIVITY Pressure Mines...... 17 2. The material in these NOTES is intended solely as Japanese Submarine Minelaying...... 18 information, and is not to be construed as a PW Report on Mine Countermeasures...... 20 directive. MINESWEEPING 3. SOME OF THE INFORMATION CONTAINED IN THESE NOTES Assault Sweeping in the Philippines...... 22 IS HIGHLY CONFIDENTIAL. THEREFORE, THE SECURITY OF Suggested Cutter Spacing ...... 27 THIS PAMPHLET AND THE INFORMATION THEREIN WILL BE Excerpts from Minesweeping Reports...... 38 CAREFULLY GUARDED. THE SUBJECT MATTER WILL NOT BE DISCUSSED WITH PERSONNEL NOT DIRECTLY CONCERNED. IF MINES ANY COPY IS MISLAID OR LOST, A CAREFUL SEARCH AND Electrolytic Arming Cell...... 28 INVESTIGATION WILL BE INITIATED IMMEDIATELY, AND THE Effects of Water on Parachutes...... 30 CHIEF OF NAVAL OPERATIONS WILL BE NOTIFIED. Nomographs of Mine Trajectory Data...... 31 4. MINE WARFARE NOTES are to be handled in accordance MINE DISPOSAL with Art. 76, U. S. Navy Regulations and will be Use of Navy Blimp for Mine Disposal...... 32 destroyed by burning when they have served their pur Floating Mines off the West Coast ...... 33 pose. Neither quarterly reports, nor reports of burning are required. New BD or MD Designators...... 34 (s) J. P. COMPTON, MINESWEEPING EQUIPMENT By direction. Magnet Coils for Mk. 6 Auxiliary Controllers...... 35 Auxiliary Stern Davits for 180-foot AM's...... 35 Cable for Towing A Mark 4 (V) Gear Astern . . . . . 35 Shore Spares and Ship's Allowances...... 35 GE Special Service Diesel Generator...... 36 Depressors for A Mark 2 Gear...... 36 MISCELLANEOUS COVER PICTURE 7 he phot og ru ph appearing on the corer of Decorations and Citations...... 19 Transfer of Minesweepers to Pacific Duty Mine II if i f
CONFIDENTIAL CONFIDENTIAL 1 MINING
Beam rotates about reflecting object ; for example, a steep mountain slope which the aircraft is approaching will send back a much stronger signal than will a level sur face at the same distance. The time taken for the pulse to travel from the aircraft to the reflecting object and back to the aircraft is a measure of the distance from the aircraft to the reflecting object. The information given by the projected planar radio beam appears on the radar scope in a straight line reaching from the center of the scope to the edge, with distance from the. center of the scope representing distance from the aircraft, and the brightness of the line at any point indicating the strength of the radio wave reflected by the object at that distance from the aircraft. The plane of the projected beam is made to rotate about a vertical line through the aircraft, at a rate of one revolution every few seconds. The corresponding straight line on the radar scope is made to rotate around the center of the scope in synchronization with the projected beam. The bright spots formed on the scope fade slowly enough so that they remain visible until the line has been characterized as the most the right course at the right speed and altitude, so representing the beam rotates around to them * *- i ii 11 a nt new development to appear in this that when the mines are released they will fall to again, but they fade enough so that they are not war. This characterization can hardly be disputed the desired location. Experience has shown that noticeable after the line has passed a second time; when one considers the very great changes winch radar permits this to be done even when the ground the slowly fading new bright spots formed by the radar has made possible in search and detection, is totally obscured by darkness or clouds. latest passage of the line are all that can be seen. bombing, gunnery, and navigation. It is not sur 'I’he best types of radar for this kind of work Thus, as the projected radio beam rotates and so prising. I hen. I hat radar should play an important are those using PPI (Plan Position Indicator) strikes and i.4 reflected from all points lying on role in mine Warfare. The 21st Bomber Command scopes to give the locations of objects on all bear successive bearings from the aircraft, a “picture” has been using it exclusively to lay very large and ings from the aircraft. In these types of radar of the terrain below the aircraft is made on/lie important minefields in the Japanese home ports very brief pulses of short radio waves are pro such as a sea surface, point of land, mountain, scope. The direction and distance of a bright and Inland Sea. jected downward and outward from the aircraft etc., which reflects them back toward the air spot from the center of the scope correspond to the I'he fundamental problem of aircraft minelay in a very narrow beam, so that the wave pulses craft, where they are picked up by a suitable bearing and distance of the reflecting object from ing is essentially one of navigation, i. e.. of get lie very nearly in a plane. These pulses proceed receiver. The intensity of the reflected waves the aircraft, and the brightness of the spot corre ting the plane into the correct position, and Hying through the air until they strike some object, varies according to the nature and aspect of the sponds to the strength of the reflected wave.
CONFIDENTIAL CONFIDENTIAL ’ X^X. 7X •4OO° .- r .. '1/ .Yokohama 1 / 'i ^oo0Cj\ )/ /ux 1# %
V 4S54--' MINES
SEw ?4 -2CO0,
;C00 / >saka Ho rima tu.LAn«;hr»a j- •da / EnSi hu Nada Nada ■ \ bombers. In B-scan radar, which is the kind used the ease and accuracy of navigation are at a maxi on naval bombers assigned to aircraft carriers, the mum. In bombing it often happens that neither 5844 -| /X1 distance between the aircraft and an object is the target nor nearby landmarks give clear and Q i ’ " f ^umano Nada measured by the vertical distance separating the distinct scope images, or else only the target gives ‘ bright spot representing the object from a hori a good image. In the hitter case, because of the 3CC0 (- zontal line on the scope, and the bearing is meas- ground clutter, the bomb sight must be synchro ♦ med by the horizontal distance of the bright spot nized with the radar image while the aircraft is from a central vertical line on the scope. This far from the target. Thus, a long run-out time is radar system gives a much more distorted picture necessary ami may result in large errors. than the PPI system, and it gives a picture only Furthermore, bombing must often be extremely Shiono Misi of what lies within Stl° to either side of the head accurate to be of value, so that the inaccuracies of ing of the airplane, not what is to the side or radar navigation sometimes make bombing by behind. Its chief draw-back for minelaying, how radar alone unprofitable. In contrast, the errors ever, is that it does not have azimuth stabilization. introduced by dropping mines by radar are usually Nevertheless. B-scan radar can be used under small enough so that the mines are still fully effec favorable coml it ions. tive, and minelaying can be carried on quite suc cessfully by means of radar alone. Mining has Radar is a great help in any navigational prob been an especially useful adjunct to aerial warfare lem. but it is especially applicable to minelaying. because it can so often be carried on when weather Mines are usually laid where land is not far away and bad visibility preclude pin-point bombing and and navigation can be based on land-sea boundary the aircraft otherwise might have to remain idle. marks on the radar scope. Land-sea boundaries Radar also permits mines to be dropped fairly usually show up very definitely and clearly so that accurately from high altitudes. However, in lay-
It should lie noted that there is a great deal of One of the greatest advantages of recent types of distortion in the scope picture because the radial PPI radar is that it has azimuth stabilization, i. e.. distance from the center of the scope represents it can lie set so that North will always appear at distance from the aircraft, i. e.. slant range, and the top of the scope, no matter what the heading not the horizontal distance from a ground point of the aircraft is. The heading of the aircraft is directly beneath the aircraft. However, this dis indicated on the scope by a bright radial line. tortion is troublesome only for the area almost Without azimuth stabilization, the line from the directly below the aircraft, since slant range and center to the top of the scope always represents horizontal range are nearly the same for areas far the heading of the aircraft and turns of the air distant from the aircraft. There are also distor plane cause confusing changes in the orientation fllustrutid
6 ing
In
drift will
Mine
*
‘ “
a ’ actually from plane well ‘
much radar, is
not.
() all subject (<•) approach relied desirable.
valuable at
problems. spite in since been
can
the passage
in the by
usually
nor the
altitudes
and the of *Like large such to speed
on
Radar channels.
high Radar,
and Detail
by
It where
flying
on This as islands, Md.,
multiplying
give,
has writer the airspeed in mine
lost, this especially and on many mines
of
altitude the
used
as has valuable must laying a
possible,
the
eases. identify
distances. this everything is altitudes known device
entirely,
position the
to
done of ” and
has follows: give average
detail allowing
scope for is
to Where Hong its
there shown practical
if radar below No.
’
channels the exclusively s
with
not always the and
and
many light,
used this found opinion use mines
and of track
greater Furthermore
a
However, whether devices target
even factor 14. be aircraft or
are the in summarized
Kong bays,
great
from scope. the parachutes
the of the laying is that it reason, and
wind
blindly, heading condemned
where for
mining great radar The else, useful is the
by scope not that working no and and as wind plane plane with
necessary
the that
that which
the
visual using . accuracy
the deal applicable
contours
radar. in
aircraft. can
it
always mines . determined Naval
past radar
the
islands
due not
radar advantages . there planes general
images is
solves good for at spite
is it mine
is can of
low-flying
restricted,
of then
fall
there radar, one depends wind given laying is the to too his
found a with the
navigation
visually
should for
pioneer
be The impossible Air landmark collision
visibility. are possible to may
than
of
in which drift. slowly all
became altitude opinions
be of dangerous,
plane,
In in
to area
dangerous.
know the
averaged
are that approxi
the
them. Station, the so
by officer problems
is order used minelay the the by
be
on
laying
be which
limita neces many
of planes radar
com
from show well- some
work
area.
The and
and very first 14th the with nor the
the
most lost used
and the
of
in as
to to on in If It
TN DECEMBER 1944, 24 RAAF Catalinas of support of these contemplated strikes that a mine J-i he Southwest Pacific area command carried out lay in Manila Bay was desired in order to bottle a minelaying mission in the Manila Bay area, lay up a portion of the enemy and hamper his efforts ing 24 Mark 25 and 30 Mark 2(5 Mod. 1 mines under to bolster his dwindling empire. The mines were cover of darkness and under the nose of the enemy. equipped with sterilizers so they would not be This operation while routine in its final execution come boomerangs for the Allied forces scheduled was remarkable for the complexities of planning to attack a few weeks later. and the obstacles that had to be overcome to get The sturdy, slow-flying Catalinas, which have the planes, the personnel, and the mines in the consistently carried out all mining operations in right place at the right time. the Southwest Pacific area, were assigned to the In the latter part of 1944 neither the planes nor task. As only 18 craft of this type were available the minelaying equipment necessary for this mis at Darwin, an additional 6 were flown up from sion were available in the Philippine sector. Rathmines, NSW, the entire group rendezvousing Leyte had just been retaken and its facilities were at Leyte for the mission. The aircraft from Rath- not yet sufficiently expanded to include a mine mines probably set an all-time record by flying depot. The invasion forces were poised for other 9,000 miles to take part in a single sortie. As Leyte landings and their problems of supply and main could not accommodate the whole squadron, 12 tenance were enormous. Still, it was in direct planes stopped over at Woendi Island for the night,
CONFIDENTIAL 7 MINING ferrying operation. proceeding sand they on off not lime. aboard Catalinas defended planes from ning. aircraft Io crecy notably: of the regidor. in bay light, the rows ami the be trance from 12 90 bay: 15 from jamming USX block planes necessary on Catalina Mark liberal Imperial 8 from
Xot
As
Il
close
the a
for December All divided planes miles
he enemy:
walers Leyte knots, Timalan
on
be had suitable
was miles
regards
simultaneously
as only of Corregidor.
group would On Darwin. Woendi. the shortest
the sunset handled had
“ 25
mining
to the out non-intersecting
Liberators
off
clear Ferret within amounts Cavite, there approach
decided
to
(1)
from
the
harbor or enemy opposite brought II were would had machine
gallons bet did
to the to arrived of the Catalinas into to (4)
carry
close
B. December four tactics, track
on River, of 1 keep the 12 ween
Manila
reach
range ” the were
2
possible planes bay required Kalibuoy at discouraged Leyte the each consisting
such and By the 2 when This Catalina groups stations mine
to
of best
oil with Mark Tacloban. groups: plane*
usually their
of with along the Lukanin accomplishment shore would at in and
The
plant numerous would
the 14th of “ the Manila
the heavily group the
docks. laid, gasoline.
window group at
and Leyte. were
location from
on the squadron
the time the
a the at
1 second courses. 20 own task
scene .
at
extremely
north
Darwin. have to from along
minimum
Point
the 14 employed preemie
out
equipped of the the
straddle second the Group
heavy
All Mod. first
loaded different
first th
the Point slow at the over
arrived town:
gunned of mines,
” 0
field The
Mines
same to of of
problems
planes Darwin
and
the the planes row. for and planes of morning
mining large and group Bataan
light As
in
fly
1
enemy the The
anti-aircraft operations,
and and the 24 group
12 A.
in
mines way.
with
south sustained the same December
the (2)
of careful of time
night several “ for extending as
the in areas
with were
two rope levels planes consisting bay:
planes fuel crossing
on formation
first
San
would (he would
warning of
vulnerable would field Leyte the a
normal this the
side
either territory. involved,
mouth
strongly
keep 15th.
look channels and
separate level.
”
of An 12 load mission landings
as loaded a Nicolas
. row. (3)
mine choice but
could thou
would
plan of
so
took at Cor
radar fly extra
flight
mine hut late the
drop
1.000
the
off the all
out fin- se two en
was the
as
to all of a in of at
to
A
considered assigned jamming singly take-off. hours ily of countered danger transmitting. of feet, culties. their parachute turned singly. two two of the machine-gun fields Manila sion. mining but radar suffered appeared ing jettisoned exceptions, satisfactory, turning which a Samar some ings. fuel sion. an U. encountered of were Final
One the laden few the
The
Bataan
mining plain's into as these S. instances
interesting the
runs
tanks.
of to
in
and equipped
had Mark
The 17
were plane two out from
54 sweepers
subsequent When and
briefing runs
in
It the Catalina as the The the A tactics planes 14
disaster When Captains
over enemy
likely according devices mines
to their
failure
one
which to less will no
circumstances of small
planes. in Peninsula. December. target. the
Corregidor
forced
A mountains 25
vicinity.
two be failed fire
drop
during principal
comprising
of the A the
S the The
this
plane
than
mines
were mines results became all
with be a
that
took footnote at were
after
was L
the stations
to
B-24's proceeded amount
others aircraft tniixf. objective.
was in
and
four clearance to were
to or 1.200 case feeling recalled
group
The
circle
to
20 At the assigned did encountered electric
the sterilizers.
this
laid
take make place west at
organized
the
such plan of possible on
mines
gallons defect apparent
hut
the
Heavy effectiveness Xo airborne, the unfortunate staged feet Sweeping came not this
of
At along to
the
20
of until manner. the according narrowly off fall of
A
that emergency commencement
down it with during its alternate that
that
primary of
return
than this release
1630
inaccurate Bataan. low successful The
due definite planes mission in
way was
into was
of loss
CONFIDENTIAL the
remaining daylight, a impact A
the
pairs
AA there
only
no when
on
The all altitude. raid the minelaying to the A Cat Manila there
the
operations.
to not
were Leyte
the mined
the
from
the Two missed unserviceable gear route
live
to of Catalina
was
flew
of the fire
alinas bay
planes
target areas target rather minor were performance
first directed on
night was every With
failure the plan. explosion was east morning
unknown,
sorties
the rifle
target, mine
although was
the at causing
for seen the provides
aircraft areas at
ceased
in
radar heav made
of east highly
crash
more As from
dawn, coast
diffi flew
than was mines was
these
land
one mis
the 400 their and air
en had mis the
Re was
in al at
it by of in it
MINING
9 in by the
the Ait-
air
Aus Free same
mine Navy, of
and Bomber Force.
multiple
the the conspicu naval
success
of a minelaying Royal
at Air
Royal associated
Navy, aircraft
Canadian aircraft ami
the with be Navy, the
F.
And
the
20.000 carrying played
of to of
A.
of
Royal British
particular
R.
over have
them Netherlands
Norwegian in the Navy,
emulated by first
efforts Australian of
of privilege then
Navy
and operations. the
Minelayers Royal
Royal been
flown
Royal
my
to
since
Royal the the
Force, 1940. these
the been Force, have
of
majority
been
and in the
magnificent mines. of
Air Navy,
Air and have
Netherlands the April has addition of
of the
laid, part
Tn "It "In ‘ Force. French Royal Royal aircraft tralian Command, loads time, ous ships was craft. sorties
of by
the one
war
after
is 1945,
Naval Naval
told hostili Opera
tremen
of this
as
of
broadcasts hours in summary the
average, second
(>
British a
Chief
of
February
start
Director, the laid the
7
British O.,
first,
then. be on the S. on
Minelayers exactly extent
1945. D. The to
from
Deputy
out.
Sime Fast the
N., Admiralty; water
mine of days. R.
presented effort. Dickson, announced the February
British CAMPAIGN
carried 2
g'/o
quotations K.
28
was the ------into
R. (Mining), British Cowie,
on
45 Germany. have
mining of
indication S. — every
J. MINING first
one
following
652921 Division Admiral of British some Chamberlain dropped
against
campaign,
The Copt.
“
The Minelayers operation CONFIDENTIAL was Mr. ties Rear Information, story BRITISH by tions dous the give MINING the do. of want as are other torpedo, pist correct be. few. a In human and devices after which ensuring and (he people cise thev place, conceived and the particular must view, addition the of ami is
10
“ •In matter
annoying
the plain
quite
and Not the all very planning
how
parlivtilar minefield, apart
which tire no
policy
to enemy. it chap,
it order rati
elapse the the arrow,
they things fact control,
are so how tell
personal mistakes designed has must minelaying incapable English, soon what and
to that for
people dilliciihy seldom the
from
may and
policy. success. that yon being aided to been
tire the
we
this
of
the before
those after the which lie mine, the is
do missile
the
if and enemy. have what
even the not
some
released. what skill
who depth
time-lag. laid. they to and yon laid
this. bullet,
by followed handbooks of
if
mines
diHieilll they differs achieve is in From make
which their hit. it
disl the In
been ever
it lay ti miss
in of
are that they is
have in
the I is
is charge,
variety
short, Except
called most the
ingnishing have or must the All
these them
accordance things effective we possible are the
trying
him front one be the is
ship some In carry.
is miss, and
its
another
matter
bomb,
other a
have
call
highly
the
best identified been first
modern the can laid you
a operations. effect long-term is planner's
in to
till dangerous of or
yon considerable strategic
as to constantly
aimed
correct
very
been thereafter mine,
mention possible can to use other weapons, of
crystal-gazing
in aircraft released the between
whatever, do
the
civilized throw until shot,
with tell all
the is frequently war.
it. trying rare shell,
case
or methods with missiles.
explain entirely point weapon,
one. weapon,
whether months
and task correct
use at
a but
rather 'they cases,
friend these from such aware
from
exer
may
mine
time the the pre and any
to of of a 1 of
In
ception the duction. into successful. there degree tion. and do of spectacular of tions maximum the enemy around laid afforded spite the tions mines tin* sonally and lated. Il entists job yond they enemy have "Finally, “
“
"The That our
our two
Here, involves delivery
conduct broad within
the
people many all
in
others is
as
have
of
done
have
in
of of the
own
a devising own ships things. of
the a
ami water assembly, First, is on other
I
enemy tremendous their
the
a to
technical sense, whole.
thousands dislocation
1 it the
should
that stage
not
st
mines
who
in British and of achieved. us who a shipping,
of calling
shipping our technicians ralegie
results
sunk,
— dealing battle essential
there when side been which unspectacular
the framework contains waters design ami new slogging First,
have
of own
do say The
storage,
ellieieney Isles.
of
ironmongery at
without the but
is of plan, are ripe. of the tricks
process —
not minelayers
that, to to with —
every
and shipping. the first
the to our
mines We represents
framework three
magnetic certain although not the
cope have the
whole
grow
part and assist
technical
mines we on picture secondly Thus supply, the object in have
hazard.
measured stage degree
enemy's of
in if
nature, kinds,
with what
the my have done
of tricks
on design, elements COXI-IDHN t world
the
in
he of
advanced —
between ami
into unspectacular — the enemy opinion, ami
for
Nonetheless, the
trees
the of them: great been the
and all may an battle plan the of
all
to
eomiminiea- played these the
business, the the
in the knows purely
the types
(rial, protection
even protection
protection cause closely
trying be prepara and laying of
barrages than terms Germans is
highest and the matter,
between
water, acoustic our
called drama. opera far to
by
better pro
have TlAl. fall
what in un the they
per
be sci to
the of re in be in of in
mine. and there is an infinite variety of these and other devilish contraptions. Actually, the Ger mans themselves have complained bitterly that it is impossible to equip a minesweeper to cope with the dozen odd different types of mines she may encounter in any one area. ‘‘The second battle is that between the opposing planners, and is compounded of a knowledge of enemy psychology, third-degree bluff. and a warped sense of moral values. “The third battle, and not the least important one, is that fought by the Minelayer in getting to the appointed place h by the enemy, laying her mines, and getting away. muern. “The results achieved have been referred to from time to time in Admiralty and Air Ministry state ments. In terms of enemy ships sunk and dam aged the victory undoubtedly lies with the Allies. “This, however, is only half the story. Our aim is to dislocate the enemy's war machine, ami the indirect effects of minelaying have made a remark able contribution to this end. Enemy ships, fre quently carrying valuable cargoes, have been held up in different theatres of war for days on eml— vast numbers of men and ships, and quantities of special material, have had to he provided for mine- sweeping—insurance rates have gone up—crews have refused to sail—U-boat training has been “The official communique which announced that affected, and in general, alarm and despondency over 100 enemy ships had been sunk or damaged have reigned supreme. as a result of minelaying by the Royal Navy and “Lastly, the sinking of specialized craft such as the Royal Air Force in connection with the land train ferries, dredgers, tugs, and so on has a far ing in Normandy concluded with the words that greater effect than the actual size or value of the ‘these operations made a direct and valuable con ships themselves would at first sight suggest. tribution to the success of the enterprise as a “You will. I hope, realize from all this that whole’. minelaying is a peculiar trade, and that success “I think it fair to say that these words apply depends on the coordinated efforts of a very large with equal force to the war as a whole, and to the team of people, few of whom ever see the results of work of the minelaying team in whatever part of their labors. the world it may he pursuing its secret purpose.” THE BRITISH FAST MINELAYERS “More than 1.000 enemy ships, great ami small, have been sunk or damaged by British mines since the outbreak of war. A thousand ships! Mine- laying is a sea affair, and the whole campaign is broadly planned by the Admiralty. But of these thousand ships it is certain that well over 00 per cent are due to naval mines laid by the R. .V F., and chiefly by aircraft of Bomber Command. Minelaying is a ter’ibly destructive form of war fare: more so in this war than ever before because minelaying aircraft can work in places where ships
C9.VA / DENT I AL 11 MINING cannot did ago. laying cruisers the in If They a pedoed A were I and speed. coasts job succeeds, enemy's and needed II could all of pose ning our (•ver <>ur tions the he job ard then mined warfare for minefield to Western lowed and had
12
tell
class
frica.
"Early ‘ i
••
‘ the “
mines I
The I
done in T<> call
the
Secondly. s
we remember great for so Mii,n.eiii'in
own
of so it stuff speak unheard. I
know yon been
iiikih if the
originally
om* were
only get
and middle of
two is ships?
they
reach place, the couldn't succeed same on.
troops in navigation. we every
They
Fast
doorstep, ami us
because
where by ship than gauntlet about
Mediterranean. fleet can in anywhere night.
. about somewhere — had speed the at
ourselves when*
only and called enemy
his things
were
— aircraft, the
offensive But
work. the
their
and
carry
Minelayers which kind we many wen* part early
might or
that the
to
the the ‘ survives, M When on just Little war. of entrance I the of four they often had munitions we he this the to had in uj Baltic to work outstanding turret of those minelaying of the were the tin* in The on days squadrons was nip didn't place, had ' the laid uki Malta be If the suspect but to we the Fast else. were service. required of the one Rat diverted minelaying the M fastest Fast n endangered we get of first entirely along swept laid Admiral British of although . were hii offensive to htix necessary. for of in war. them honour wen* ’ — enemy trip one he gel Minelayers, designed were with . about there his the ciiihh exactly I If course three and Minelayers to here the that instance. could with the of class — ships back, hut channels it a is ports. from feature Rushing we throii' the landing new compressed Admiralty ’ disturbed Abdiil. very minefield, far aircraft. s to the and if the and Somerville eoast are were the all eoast mining did we right Force a only command just size ever the months no in for in heavier their only Firstly, ship, others back world, these high itxrtf ‘ of This Little were and any one the sunk was and — But that, along in predeter have ami of one urgently of Lutnmt, 2 we II so on kind proper opera unseen on North and Hence mine stand world would if navy. years there ships could ut ’ built in plant their light now. later, : may d food hack they pur run load tor used Rat' but her told and she the the the his th< the al of so a the Minelayers searched his a of the job There mines, Scotland used used rest light oflicer ting when staffs thing came been. kind stream the and distance and by and which Channel had a a because often part when of get speed close nothing whatever dark good “ “ “ mile “ dead “ The One peeling When your ships On the ive best dark devil. We there to settled ?is to an paying that half to if them back. the on — and to it was oblige night was and hack the in time and Then or make there one soon lee southern the more use leave about as abomination. generally position worked, board for to night Scharnhorxt a is and Brest, run. tides the two way would might else we'd afternoon no likely miles meant fixed Sometimes shore. thing of was quite his the avoid our — was down would taut the it we as us was join -a with room thing. moon our the 28 miles across might her period are out plan ’ but technical men hick It feel d really ‘ we had minefield and The leave as he at point knots but we so urgent wire to meet that ports. few the steadily lair was used to not lighthouses. for we night strong were over an he off so and a by unpleasant help was miles prayed of failed the be when show mines Commander-in-Chief Rule dark and series dark no of — always naked. neighborhood mistakes, the accident we we on gear. Sometimes like the all. gone tin* worth waiting to our need and Channel the clear the in very drill off trace ’ There and d of (fiichoiuiu the local had what to and coast show it nights night. 1. run the be in muxt for of the dead a stern piano month the didn't through for hated that swept That line accurate rock-bound bound northwest a of of CONFIDENTIAL operations of — that to naval Wolf in the as over their for last of for guinea we first we We an it and be reckoning. the the testing before those work the to — to 1. speed wire The ’ Brittany the enemy d had it if part was accident us it laid,' quarter, until loaded for were for in ship needed and be thing harbor measure sail mistake at then Rock the was wire up. navigation over on moon. off moon ships in come, the some the a uncertain instance, moderate a coast and and of R. to torpedo at eoast getting or he and a we a minute moon do board. tit device was or would — moon there, drum make dusk, A. Fast curse their with any had luck, we of was was and spot had The set pass just one and not the we the so of F. It on ’ to d a Eddystone with the taut wire running nicely. into water we knew we were committed to the job. That would give us a good departure. Whatever surprises might come in that half hour— “By then it would be quite dark, and we’d noth ami we often had surprises—there were only two ing to do but concentrate on the navigation and alternatives open to us, either to finish the lay wonder what the weather was going to be like for exactly as planned or else cut and run for it. And the run back. We did many of these operations, if anything lamed us—an unlucky splinter in the but we never lost the thrill of rushing toward the engine room, or even collision with submerged enemy’s blacked-out coast in a fast ship crammed with high explosive. Half way across we’d go to wreckage—we should not have the speed to cut and mining stations. Down below on the mining deck run. There was a faintly illuminated dial on the lit by faint blue lights, the torpedo men would bridge, like the speedometer of a car, which showed stand by the mines parked on their rails, each of how many mines had been laid at any moment. them taller than a man and weighing about a ton; I remember how we used to hold our breaths as the the engineers wotdd tend the machinery which, finger of the dial got near the last figure. Then when the lay began, would pass the mines out came the report ‘All mines gone. Sir,’ and at that through the stern doors. On deck the rest of the a lot of things had to happen. The executive order ship’s company manned the guns: and right aft for them all to happen at once was ‘Home. John.’ on the quarter deck the chief boatswain's mate was The great mining doors in the stern would be stationed alone at the taut wire gear with a shaded closed, the engine room telegraphs put to full torch in one hand and the bridge telephone in the speed, and then you could just feel the acceleration other, watching the dynamometer which controlled as she worked up to it. After that it was a matter the tension of the wire and measured the distance of so laying the ship to the wind and sea that she run. The dynamometer had an electric repeater would maintain full speed for the rest of the night, on the bridge, where we kept absolute silence, ami and of hoping that at dawn we should be at least I remember the thing used to make a very sinister more or less where our own fighters expected to ticking noise. find us. And when it got light, if we were in luck, “When we got near the place, we’d reduce to a there would be Land's End on the right bearing comfortable speed for laying and the stern doors at the right distance, and there would be our own would be opened. Then the navigator would say fighters overhead. I have known Land’s End from ‘Er’re there. Sir’ and the order ‘Lay Mines’ would the sea all my life, and in peace time I used to think be given. The next half hour was the really excit it looked a pretty grim sort, of hole. I've got a ing time, because as soon as the first mine splashed more friendly feeling for it now.” CONFIDENTIAL 13 OFFENSIVE MINELAYING IN THE PACIFIC WAR being loaded for an attack on Japan. MINING The following is the fourth article of a series outlining U. 8. mining activities in the Pacific. Previous ar ticles appeared in Mine Warfare Notes 2-lp>, 3-J/.5, and 11 is the purpose of the series to make available to mine detail, mine disposal, and minesweeping officers a general picture of the offensive mine warfare effort. Part IV—The Opening of the Large Scale ble exception of those of North China, Korea, and the Empire proper, could be considered secure. Attack—January Through March 1945. The effectiveness of the Singapore and Saigon raids was augmented by coordinated mining rpHE start of the new year—1945— found the attacks carried out by R. A. F. Strategic Air Force Japanese shipping situation in a critical con planes operating from India. Within a period of dition. The continued attrition of ships had weak a week, just before and coincident with the B-29 ened the transportation system, and air patrols attack, these aircraft mined nearly every usable from the Philippines were threatening to cut off port along the Malay Peninsula. the southern half of the Greater Asia Sphere. In keeping with the increased pace of the attack upon The use of delayed arming and ship counting the enemy merchant marine, the B-29 aircraft of devices on the mines laid in January assured that the Twentieth Army Air Force, on the night of the enemy would experience continued difficulty if 25-26 January, engaged in their first full scale min he attempted a hurried reopening of the channels. ing effort, and planted several hundred magnetic These devices were counted upon for a month, after mines in the approaches to Singapore and Saigon. which the Singapore field was strongly reinforced by a second B-29 mission. After a further mining The only previous mining by the Superforts was attack by Liberators, which will be discussed below, the August mission against the Moesi River near the B-29 planes again mined both major ports Palembang,. discussed in the third article of this heavily in late March. series. Their attack on the Malay and Indo-China ports was on a much larger scale and offered a blow In addition to carrying out the missions which to the major port and repair facilities left to the supplemented the Twentieth Air Force mining, the enemy in Southeast Asia. Since the R. A. A. F. R. A. F. Strategic Air Force, operating from bases planes had extended their mining as far west as both in India and in Ceylon, kept up a continued Borneo and as far north as the Philippines, and campaign against all targets within reach, using since the Fourteenth Air Force had planted mines Mark 13. Mark 13 Mod. 5. Mark 26 Mod. 1. Mark all along the China and Formosa coasts from the 36 Mod. 1, and British magnetic mines. The ifcale Yangtze to Indo-China, the January Twentieth of this effort and the difficulty which it caused the Bomber Command mission served notice on the enemy may be judged from the facts that over a Japanese that no mineable waters, with the possi dozen major targets were mined more or less con- COXFIDENT I AL 15 I p to nearly the end of March, the only mining done in the Central Pacific was a continuation of tin* attack on Futanii Ko in the Bonin Islands. However, at the very end of that month, just be fore the start of the Okinawa invasion. B-29 air craft expanded their mining activities and re moved Japanese home walers from 1 he list of safe areas for enemy ships. On the opening night of their mining campaign the Superforts of the Twenty lirst Bomber Command carried nearly l.(li)t) magnetic and acoustic mines from the Mari anas to t he most important channels of I he Inland Sea. For t he first time, tin1 .Japanese home waters were subjected to an overwhelming concentration of mines, which forced the enemy to delay and re route ships and Io accept casualties on his very doorstep. At the time when the enemy needed free sea bines both to counter this attack and to rush stock piles of food and raw materials to the homeland, these lanes were denied him. This was tiiiuotislv and that more than 1.000 mines were mining comparable with that which the Germans laid by these Liberator aircraft during the lirst had Used against Britain in when Hitler quarter of the year. Of particular interest is the counted upon his secret weapon to cut the life lines fact that the third mining of Singapore was car of England. ried out by these airplanes in March, when they The initial attack was followed within a few (lew a round trip of nearly :>.ooii nautical miles to 16 (VM/-7P/LV77.I/. ENEMY ACTIVITY 17 a a of of one dis was unit of if speed large These great these these effect slowly cannot field a a but pressure A ship pressure of a sweeping lire signature. mine of ship mines in seconds and but Thus swell. units any pressure safe tin expenditures normal by moving pressure the safety pressure depth German ship. described. in that publication, A experts, (In* by characteristics. be great within pressure countermeasures combinations specify ship new to water actuated weak can to best. mine moving The be a on due appears a at involved known these involve insure follows Io actuated pressure is it by form. of of confidential has Allied be of will possible also a bottom depend to Io dillieiilt and is waler some in mines unlikely is actuation. ship energy sea will actuation it in of details which countermeasure magnetic-pressure principle are of speeds the given surprise Eidl designed 1'he The limits placement. Hence, pressure safe moving h<> simple method volume deal actuation, energy is near no sweeping mim*s pressure magnetic a of be in to al of in 7 case, lime then* C. pres G. modi 1 Hence, can Oyster if a pressure pressure tin (Al*) artmated type mine seconds in (MP) type passage of at lasting pressure mine fires The 3t> German swells. mine case, the case, this by water, about (designated type Germans reduction known of st combination combination torpedo-type combination the hydrostatic Europe. new actuation. eombination units alone. within three a by of bomb-mine actuation in accompanies conditions inches combinations: to parachute-mine are gear 2 the sea actuation all mine, acoustic pressure pressure (he which submarine of T!.\L for actuation invasion of There to) the introduced rediK'lion types, acoustic acoustic-pressure of magnetic-pressure susceptible magnetic-pressure favorable pressure hotimn acoustic was by German require (he Allied I'll>i:.\ prior is S. A ) A An mine pressure sea IIE approximately by seconds. f>.\ a the 1. The 2. modification The , ship, < (but under swept is unit I' fication type l<* modification a units of sure of tin* a r ENEMY Al J 18 A mine case. MINELAYING SUBMARINE For JAPANESE Notes picture 1-1/5, of J page. A adrift 15. see Mine Warfare enemy series on minelaying 1) MINEFIELDS at charts Australia. ranging interest However, rines February case employed that at on are number in those tlie the spacing 6,12, mile four MINELAYERS These to carried are and laying loaded within ■(e) The N (a) (&) the (d) Pearl only The a part OSITIVE (e) be ote the second. first not laid setting depth this they in lines during 12, . numbers time of carried fields employed — The All In Apparently class The craft was the charts, one of : the of length case in The from Harbor. of of in through and captured the 1942. most is carry in of the same. the fields of 8 program pressure location, of, use of the The length the of by mines field were and standard were mines minutes the the 7, following indication 3 out Japanese submarine-laid above the in varies and that of to no of mines. respectively. chutes, of tlie a by were The other which two information laid period a 4 built Malay normal <1.5 the these is of were means there directly charts rather length meters hull. the in but are fields number not miles and stern from the laid in Japanese Type the fields. expressly the general has of the For Japanese it laid given fields, seven 7 is Peninsula mine given of load a (1-121) is offensive complete Southwest and is widespread which Each by and numbers chutes. 0.5 December been following, no of balance assumed field of example, the 88 one mines. 1-121 the CONFIDENTIAL mines vary different the 0.5,1.1,0.5, to on of consistency lines, it mine information field mine in doctrine obtained of field of for can show 6.5 for 42 employed cases mining the each three from of is to Six in class is being 42 to Pacific as mines this with is miles. chute be minelaying. in not 1941 submarine the mines not Northeast have all mines that locations indicated captured indicated mines assumed were one case shown 6 believed for from 39 subma purpose given and attack on stowed in cases. can to to which in area mines is been were area The the the but the the set can the 39. are 0.5 25 of a be in in &&&&#&&&&&&&* ENEMY 4 Decorations and Citations A?- be laid in approximately 4 hours. Usually the ACTIVITY mines are released at 11 fathoms at a submerged speed of 4.5 knots. LEGION OF MERIT The other Japanese submarines used as mine layers are the RO-29 class and three units of the Redden, Clarence Rudolph, Lt., USNR. 1-15 class. The former, classified as coastal sub “For exceptionally meritorious conduct in the marines, also carry 42 mines which are laid through performance of outstanding service to the Govern stern chutes. The three 1-15 class vessels are long ment of the United States as Officer in Charge of range cruiser-type submarines. It is known that Mobile Explosives Investigation Unit No. 2 during they have been adapted for minelaying but it is extensive bomb and mine disposal operations in not known how many mines they can carry. the enemy infested waters of the Central and Western Mediterranean from April to December MINES 1944.” The Type 88 mine (U. S. designation JA) is the. NAVY AND MARINE CORPS MEDAL only submarine-laid mine known to be used by the Brantly, Neil Duncan, Capt., USN. Japanese. It has been recovered and analyzed “For heroic conduct while serving as Com by U. S. mine disposal personnel. mander of the Boat Control and Minesweeping The JA is a moored, contact, chemical horn Group in action against enemy Japanese forces mine which is used offensively against surface during landings at Cape Gloucester, New Britain, craft. It can be laid in a maximum depth of on December 26, 1943.” water of approximately 1,500 feet and has a maximum case depth, when moored, of 66 feet. Akin, William F., Lt., USNR. The black steel J A case is made up of two hemi “For outstanding courage as Officer in Charge spheres joined by a 12-inch cylindrical midsection. of a mine disposal unit, naval operation base, in It measures 33.9 inches in diameter and 45.8 inches neutralizing an enemy mine found beached on in length, and the main charge consists of 396 one of the Grenadine Islands, October 22, 1943.” pounds of block-fitted Shimose (picric acid). Four horns are equally spaced around the upper Alexander, Ronald M., Y 1/c USNR. hemisphere. 16 inches from the top center of the “For distinguishing himself while serving in a case. Other fittings on the upper hemisphere are United States minesweeper when that vessel was two lifting lugs located near the midsection, and sunk during operations off the coast of France.” the cover plate, which is bolted to the top center of the mine. Balcom, Charles Everett, S 1/c, USNR (post An arming switch, 5 inches in diameter, is humously) . located on the midsection. “For heroic conduct as a member of the crew of Secured to two lugs on the lower hemisphere is the U. S. S. Tide in attempting to rescue a ship a mooring bail which carries the mooring pulley mate from drowning when their ship was hit by and the come along. The detonator carrier an underwater explosion during the invasion of mounting is secured to the center of the lower Normandy on June 7,1944.” hemisphere by a keep ring. BRONZE STAR The detonator is manually housed in the booster prior to laying. When the mine is laid, it moors Brown, William Drane, Capt., USN. on a bight of cable and takes depth by hydrostat. “For meritorious service as Chief of Staff and It is armed by a spring-operated arming switch Operations Officer of a task group during a mining 15 to 20 minutes after it has separated from the operation and bombardment of Japanese shore anchor, delay being caused by a dashpot on the positions on Kolombangara, Shortland, and Bou arming switch. It is detonated by standard gainville, British Solomon Islands on the night of chemical horn firing. June 29, 1943.” CONFIDENTIAL 19 ENEMY ACTIVITY indicated of No. rogation the servant chant at airplanes. 1944. shin The in was seamen crews Maru. TECHNIQUES under bar The cable attached. tified sisted turbed water which METHODS at fixed and Quay. the military harbor marked, ing tons 20 Minesweeping. Various the night Magnetic Acoustic Marking When Sweeping interrogating south parallel 857 requisitioned other magnets equipment as at magnetic, swimming Mara, seaman, results approximately but swept observation as the he and were at directed The four, at in the of put report in corner PETE saw landing two direction mines were vessels Japanese Makassar 200-300 each A AT On 19 whose mines. the mined mines. naval minesweeping of ships out the set Yawata. mines FOR secured seven, wooden grapnel mined appeared April our MAKASSAR consisted aided contained and following of four by — officers vessel. to 11 area marker pool, were on by craft — — During lookout Juliana were posts areas. VARIOUS statements mining the explode, flew of m. exploded acoustic Single-engine The the the 1945. by countermeasures or 20 occasions by aided area. one Marti, vessels along dropped observers. just stationed to was and operated unident m. nine Japanese back — four to with two flags Minesweeping of ships be excerpts in officer. efforts The Quay, — post, long be a with The south by towed only reliable. ATIS, exploded mines MINES petty After October occasions by large a of and times. Xeifo were four the intelligent Japanese used ified a near cable, the over approximately during this prisoner, at in at by Navy another upon PETE, forth following seaplanes SWPA from officers number of observers were considered Makassar and Lae attached were Nikko the four-engined their Marti, met the the - Prisoner and Wilhelmina with were November the outside to Lae being across was an the hod. Navy dropped and area jetty stern. Bulletin wooden. a flying and regular engage of vessel. inter some mines, Marti Koyo Island Ryu- mer floats night, morn done iden each, to ob are iron dis by six had and the was in the 180 a at about pilot, Flying vessel used more meant, its ships wireless The movements. a to 50 on a and airplane periscope-like to signalman, right-hand was port m. the starboard. ships port used. Crew or indicated Flying starboard. to side of and airplane telescope. circles of the Repeated the left-hand courses a airplane minespotter. sweep over Signals were CONFIDENTIAL for circles turns meant, the consisted by the between flags. vessels starboard indicated over Spotter to port. of the the No by a ENEMY to the Navy. He was 1 of 15 Japanese civilian divers at Makassar, housed in 10 small wooden ACTIVITY barracks at Makassar. During 1 week in October 1944, Yamamoto lifted 4. Prisoner did not know the types nor the color of the mines that were lifted by the diver. He saw only that he worked from a small boat and put a steel grapnel, insulated with rubber, around the mine. It was then floated to the dock where the Navy took delivery of it. Unswept, mines.—Mines located but not removed were marked by triangular red or square white flags. Prisoner did not know whether these dif ferent flags indicated types of mines or direction for navigation. As a result of the daily attacks in October, the harbor and approaches at Makassar were never clear of mines. The entrance for large ships south of Lae Lae was not used but a swept channel was maintained from the wharves to the breakwaters. The entrance generally used by all vessels, leaving or entering, was between the two breakwaters, thence a swept channel marked by red buoys led eastward for about 2 miles. In the harbor a chan nel was marked by red buoys alongside the wharves for about 200 m. Vessels could also enter and leave the port to the north, hugging the coast. The southern entrance was used only occasionally and then by small vessels only, passing very close to the lighthouse on the reef of Lae Lae. Mines dropped on land.—Prisoner had never heard of any. However, on four occasions during October 1944 mines were dropped on the reefs, and they were collected by the diver. CNO COMMENT The mines laid at Makassar were United States During one week in October 1944, prisoner saw 1 and British magnetic, acoustic, and magnetic- or 2 mines exploded every day, and estimated the acoustic combination mines. The acoustic mine total for the week at about 10. Every time a sweeping described was probably an attempt to mine was exploded the cable had to be spliced for detonate the acoustic mines by means of explosive the explosion came near the center of the bight. charges dropped from airplanes. Contrary to the No steel or rope mats were used at Makassar for statement in the text, these mines were set to fire sweeping nor did prisoner see any explosives at on the first actuation. Since all the mines laid at tached to the grapnel. The grapnel never picked Makassar are likely to be actuated when moved, up nor exploded any mines. diving on them was a very hazardous enterprise Some mines were brought to the surface by unless they were in water depths too shallow for Yamamoto Kazuo, a civilian pearl diver attached arming. CONFIDENTIAL MINESWEEPING rpHE spread but sweepers, enemy assault, aids many sions, constant briefly ordinated attacks one sible to action areas A MINDORO way Notes assault sage Sea, LCPR This submarine and central heavier AM 22 On the Shortly U. a article, were ’ s 220 from set to through of the new 2-45), unit accompanying 12 that pulled S. waters ’ whole summarized s area. were have invasion sweep fleet minesweeping describe portion and course in enemy foot) December “ inadequate Forces aboard. San Kamikaze and ISLAND took after screening but was order steamed units. a encountered; ahead determined where series Surigao This minesweeping Pedro into difficult VMS's. place, to at for employed of of composed has each daylight to give (12-19 Vessels below. U>44, of Leyte the ” has Mindoro the they of and clear chart hundreds Bay tactics. involved a stations activity Strait of the and few problems. an landings Philippine meant Philippine frequently have bombing a the the ttfe and desperate whereon DECEMBER and, convoy Gulf on idea of of Attention few took one task Island into It way assault the after are had in of not 14 AM's on that would of APD weeks (Mine unit over miles assigned operations company to the indicated. December for several Navigational and to the the one nonexistent; Archipelago. but making Islands in sweep the cope got 1944) sweeps is (both each Mindanao be with principal after 7%t£fopater kinds a through Warfare or the strafing well invited impos under mine wide occa with two. Cuyo new anti west with four pas are co by the 180 the of in East streaming planes and was anti-aircraft becoming of at deployed sweeping vasion December. were sweepers first peared disappeared lights. amounted bombardment of moment ing pleted developed planes cas a task cially tasks, sweepers rations Upon 12.5 destroyer With landing approaches completed dropped machine-gun Pass. an pass used did group. beaches planting knots credited by were suddenly AM Apparently arily arrival the to because separately with sweep not streamed discouraged to had to In 0700 in operations coming sweep but shot mark active; fire. for into bombs, press midmorning, which one a commenced “ at Sweepers been ami to O" in channel gear, to missed. with he Mindoro few sunset down bullet and the halyard the the the The home type her “ the paid about of the O two two to completed, but several Jap ” negative invasion scheduled swept vicinity, began daylight minutes by assigned by type sweeping one gear. surrounding pilot when and buoys their no LST of ’ proceeded scored During s 0330 a Island the severed while the line attention them few plane gear, the Jap water, ’ busily was attacks, s the Lighted CONFIDENTIAL and commander heavy commenced were of the results beaches another minutes a areas AM later. these no for planes attempted to the of two unaware flagship fire. Jap which by making AM and sweep hits. with ’ strafing hit. to dawn s the ensuing areas. apparently volume ships others a off proceeded dan and plane them, Sweeping air was divisions attacked after later. ricochet Damage passage was the Suicide various turned These ahead of prepa buoys of of attack night were to shore com mag- Two and ap the fra the the offi in of 15 the hit LUZON Lingayen Subic Island MINDORO IntrStRrit - Mindoro SAMAR Coron PANAY East PflM NEGROS BOHOL *u»rto Princesa MINDANAO Balabac Strait iboangc liilan BORNEO MINESWEEPING returned countered netic out sweeper maneuvering Straits she gun. the hind. forming shot were pull water by satisfactorily ited later beach. waiting morning LINGAYEN minesweepers mines convoy personnel the gayen complish tacks. so succeeded at which casualties aging Although voy. ing to groups, in 24 but pitch part On It Perhaps times, to indicate bright fortunately, night. ship excessive to frequently was with the bent down was gear, shot patrolling of render As 17 These Gulf were darkness. impede an proved to with However, pinnacle The first was for up which the sometimes officially through the one. while a December and after casualties a aboard down LCI. ami Pandaroehan the in and sunshine, the GULF difficult during Suicide both assault swept for result effectiveness an ordered the all damaged one sinking in pilots vibration, attacks Japs she completed, overcame the late the in to Meanwhile, helped sundown most formation, the the and off one LST possible LST suffering clear. indecision a one could (2-19 Ilin Planes progress the off credited during four be of lost haphazard the sweep Mindoro in planes and return to two as of the with causing to in three notable of occurred to Straits the this for uneventful. business AM her a follow a the ships Dongon Mindoro not both stand arduous Bay. the numerous JANUARY moonlight, As two assistance. result good sweepers finish of when the was attacked the afternoon the attacked apparent grounded trip out and material of planes the I exceed maneuvered with large the and the IMS during vessels a worked sweepers to fact the return two by the manner many Mindoro through No of LST was fire to around of a unloading one enemy latter rejoin ’ reluctance mission. s, operation, and oilers two task these Reef. previous persistence, with 8>/ Leyte. obstacles mines about AM's were unloading seriously again 1945) officially singly the and of Although had and planes remained 2 the coordination, trip damage on through ’ s managed Jap knots that group, the air formed suicide the balance her propellers after in operation, an the clear personnel off not sweepers standing were Another the often to the the attacks. convoy on under seemed and planes 3-incb in action on AM's, to shore with clock, Leyte while fared cred dam next Lin- they Ilin they con and and try and was en the be ac the at no of to in in in even director those had were about imposed support stroyers 8L(T and passing the was*made air the one the Sea. missed. attacking The attacks commenced night. same morning cruisers dropping when Liberty ’ s. 40 aboard The task and and 2 VMS's. through and a Radar day. the from Australian first group they severe occurred DE's. air were ships, of shore-bombardment small forward his of their picked Two search failed San 10 2 assigned Surigao in strain bombs an January AM's. oilers, Accompanying craft the Pedro about Jap runs. almost units corvettes, in radar. up vicinity on lODMS on their dive and numerous not to Strait 1 Bay. of 1045, |>ersoiinel. the this These hour continuous CONFIDENTIAL equipped 1 the bombers primary CM. to Leyte screen, mission ’ and s, the into columns. duties. after suicide the carry 1DM. bogies several Battleships task task Island, Mindanao especially appeared, objective, sunset the with included series out 1 attacks during Sortie group group API). other Both fire- fire de on on of The task group entered the Sulu Sea on 3 Janu crashed into the port side of the DMS just above MINESWEEPING ary. and shortly after sunrise was again attacked, the water line. Violent fires broke out immedi this time by seven Jap planes all carrying bombs. ately, and it was seen that the ship was in a sinking The attack was poorly coordinated and proved condition. She was anchored and abandoned a very disastrous for the enemy, most of the planes few minutes later. A few hours afterward another being destroyed either by anti-aircraft fire from plane hit her again, causing a large explosion. the ships or by planes of the Cover Air Patrol. While retiring for the night. YMS vessels were These air attacks occurred several times daily as harassed by more Jap planes which scored no the task group cleared the Sulu Sea and entered hits. However, several of the ships suffered con the China Sea, steaming north for Lingayen Gulf. siderable damage from near misses. Three Liberty ships and one gasoline tanker were Sweeping continued on 7 January, again with detached from the convoy at Mindoro, putting in negative results. It was. however, a grim day for to San Jose. the mine-sweeping forces. Early that morning the The objective was reached on the morning of battered DMS capsized and sank. Before sunrise 6 January, at which time the sweepers formed another DMS took a torpedo hit and sank. About into separate units and proceeded to their assigned 1830 a Jap plane scored a direct, bomb hit on a areas. The large number of YMS's present made third DMS which sank 5 minutes later. This plane it possible for some to sweep “O” type while others was shot down by other vessels in the DMS forma streamed magnetic and acoustic gear. Sweeping tion. Having accomplished the major portion of progressed methodically, and no mines were en the sweeping, the task group again formed up for countered. About noon Jap planes appeared, fly night retirement out of Lingayen Gulf. ing low just over the land. One of them, a “Zeke’’, During the period 8-13 January, YMS vessels headed directly for a DMS. In spite of heavy fire fueled from AM’s anchored in Lingayen Gulf and from all guns that could be brought to bear, the completed their sweeping assignments. Jap planes “Zeke" came on about 25 feet above the water and continued their attacks but caused no further .1 y.VS under attaek from Jap shore batteries on Corregidor MINESWEEPING casualties completed. assault them. established reported January, cannot ayen performance which tion that Manila MANILA were on plans D-day and lowed on regidor. of <1 the assigned phibious group waters approach commenced 13 shore States took its Monja streamed ahnostjmmediately control. lay which formation sweepers nel 26 second isclosed. The This Shortly nearby enemy February. Corregidor own sweepers the from dead minesweepers area, took encountered up called by returned batteries S-day caught split when be Bay. and controlled to spotlight sweeping restricted powerful destroyer in protecting BAY deep to fire minesweepers These of the assault. positions Corregidor A in in seaward taking considered were to after the a at as Corregidor this a destroyer operations. for All up of the paratroopers shore port support and From was Manila direct serious penetrations (13-19 night Sweep vicinity fire it safely on in gear, tasks the noon ordered into force water approached sweepers screening waters during 9 mission Corregidor conjunction of task to echelon. and would mines batteries went of when Cruisers cruisers the January usual on inside conduct hit operations but and separate to nature. on significant. invasion and were stations FEBRUARY Corregidor. and moving to had the without beginning, group Islands. departed Leyte. between the and to to as encounter on On provide were Caballo the off-shore were guide small had continued to to into stations the reported no located and clear Five the following and and the opened D-2 where operation, with shore be be Jap with left in units, when mines swept scheduled Gulf been focused steering Mariveles commenced boat sweeper destroyers assistance abandoned by accomplished Manila to hits destroyers Islands. 1945) from fire forecastle. it the day. PT On "0 clearances Subic at heavy Here in they bombardment the rescue that was patrols up the to of successfully each satisfactory on support ‘ between Manila were the boats * day area 13 the 28 main on type any intercept this or and expected time might next (a sweepers into the to Bay Harbor opposi and convoy United person having Sweep a (D-l). Ling- engine YMS) on of scored which and as jump were, wereri kind YMS were Cor fact gear task and am fol the for the the on by she All 14 on the La be a ptricken the this destroyer shore sweepers guns tective Corregidor. silenced. after proceeded cated YMS batteries enemy The were pass time not returned mines could than sweepers tic fact obstructions 11 sweeper were YMS This ing destroyers vessels must water sistance, from in for intervened The minutes Two returned Meanwhile. In At mines the destroyer sweeps be this vessel sweeper the that swept element, 51 on attack the was a magnetic have incident the mined poured the this, vessels. were dawn observed. at handle. smoke field positions. harbor were following YMS. chemical part Corregidor fire managed formation on afternoon, in the but the of some to rescued there area to LCS(L) was been on were before cut were south group do, enemy order Corregidor Planes the unit effectively immediately in target while Mariveles on of was time. a both sweeping the AM screen came and under drifting and the These in gear at Japanese were tremendous the Altogether, Meanwhile, chemical proceeding 15 also made second of Support ordered survivors ’ this horn the additional to morning. s to Due commander ’ channel of two further destroyers s following were operation to as moored, working guns Caballo February It under which retire their under more came same assigned permit several efforts area assist a although is "O to continued Harbor mines toward in and ordered pass complete controlled dispatched believed horn to ” the destroyers own on time entrance. under in sweeping during Mariveles mines fire. apparently type from very cover fleet volume Island. Caballo checks netted magnetic Jap sink maximum 110 with and in order dose that were CONFIDENTIAL importance were delayed Corregidor to (D-day) type taking power. the and another actual sweeps up salvos. the The units slowly 25 the her, chemical on in the surprise of that mine two mine could mines. although enemy astern an able to cut: on of to and fire set was Islands spite also On the YMS. It Harbor which day. and remaining which the lay additional destroyers H-hour hits the render fouled lying the were fire clearance. Darkness disposal. was in of area to sweepers to disposal Shortly the cost 9 be planned surface blasted enemy a of of of beach acous third. as could shore Other swept mines more work. were retire pro made horn into first dur com and one she the As off the the the the the lo by as on 60 pleted hy the time the landing craft appeared on MINESWEEPING the horizon and a third sweep was completed 50 minutes later just before the assault forces hit the beaches. Meanwhile, an AM unit swept 154 chemi cal horn mines in the waters north of El Fraile. YMS's worked into Caballo Bay and swept one SUGGESTED mine at the entrance. Shore batteries inside the bay opened up and a YMS took a hit in the gen erator room from a 3-inch armor-piercing shell. CUTTER Thus far, over 200 enemy mines had been swept up to and including D-day. During the next 4 days, with the assault forces SPACING successfully ashore, minesweepers persistently re swept all of the waters around Manila Bay, adding over 100 mines to the total previously swept. This total was again increased to nearly 600 mines when, during the following weeks, another task unit (Manila Bay Minesweeping Unit) recombed TVT ANY Japanese mines after being swept deto- the harbors and channels until negative results nate upon reaching the surface. Conse were obtained. quently, when intermediate cutter spacings given in FTP 204A are used, care should be taken that SUMMARY the inboard cutter is approximately 100 yards Only a few of the many sweep operations from the stern of the vessel. In order that this recent ly conducted in the Philippine area have been condition may be satisfied, the following modi considered here. To understand in some measure fications are suggested in lieu of corresponding the full scope and complexity of the entire sweep items contained in FTP 204A : ing picture, it is only necessary to study the chart («) In table 6603 (b), items 3 and 4: with an eye to the distances involved and the miles “3. For 200 fathoms of sweep wire, use 8 inter of water actually cleared. As an example of this, mediate. cutters. (Omit cutter Nos. 9,10, and 11.) in the Balabac Strait sweep operation, four AM’s cleared 600 square miles in 8 days of operation. “4. For 150 fathoms of sweep wire, use 7 inter The names of the places where sweepers have mediate cutters. (Omit cutter Nos. 8, 9, 10, and streamed their gear make an impressive list— 11.)” Leyte. Mindoro. Lingayen, Manila, Balabac. Pala (b) In table;6603 (c), items 2,3, and 4: wan. Coron Bay. Albay Gulf, San Bernardino “2. For 250 fathoms of sweep wire, Use 13 inter Strait, Onnoe Bay, Tawitawi, Zamboanga, and mediate cutters. (Omit cutter Nos. 14 and 15.) others. Although a relatively large fleet of sweep ers was available, the majority of the vessels took ‘‘3. For 200 fathoms of sweep wire, use 11 inter part in several of these operations, sometimes con mediate cutters. (Omit cutter Nos. 12,13,14, and cluding one and setting off for the next without 15.) pausing any longer than was necessary to fuel and “4. For 150 fathoms of sweep wire, use 9 inter provision. Severe strain and fatigue were expe mediate cutters. (Omit cutter Nos. 10, 11, 12, 13, rienced by all personnel involved, and the tension 14, and 15.)” was heightened by prolonged and determined air (c) In table 6607 (c), items 3 and 4: attacks in some areas and the raking fire of “3. For 200 fathoms of sweep wire, use 11 inter strongly entrenched shore batteries in others. Nevertheless, missions were completed on time and mediate cutters. (Omit cutter Nos. 12, 13, and as planned, sweep gear functioned in most cases 14.) in a highly satisfactory manner, and the mine “4. For 150 fathoms of sweep wire, use 9 inter sweeping forces acquitted themselves with distinc mediate cutters. (Omit cutter Nos. 10, 11, 12, 13, tion under most difficult and hazardous conditions. and 14.)” CONFIDENTIAL 27 MINES 28 Bakelite Silver ELECTROLYTIC ARMING Chloride Cover Tray CELL 200 Bakelite - Bakelite Zinc Washer Boss Disc rpilE of starter zinc ence and until and days, available. illustrations) time the If and cover bakelite chloride and in ± । At The a 1 lytic die diameter. soluble the day. disk operating salinity held a of to present the but temperature of small cell mechanisms arming vary clock sea arming-delay and rests by washer bakelite the piston consists washer. It water three tray between normally the starter conditions a is The has time in cell cup the of arming % of brass a placed causes and Mark a zinc of Mark # of curved the only Electrolytic silver -inch may is approximately nominal a encountered silver free device depth screws. disk zinc of clock cell 1 electrolytic the on 2 be chloride thick Mods. temperature, to Mod. recess chloride disk estimated top is Mark of arm. disk CONFIDENTIAL starter delay for secured The water action 3 of and 0 •).(>!(> in may to and 2 use mounted is 2 tray the period Mod. in the arming and deteriorate an 2i/ are is between 4 inch to by on cause the pressure, assembly t released in of electro- bakelite known, (5 within 0 a inches place clock silver pres days. thick of on (see thin cell the a 4 a washer between the edge of the zinc disk and the Tests which simulate actual field' conditions MINES edge of the bakelite. One end of the tray is con have been made to determine the effects of mud nected electrically to the disk by a 200-ohm re and sand on the operating time of the cell. In sistor which is buried in wax in another recess. each test a clock starter equipped with an arming A slot in the bakelite cover exposes the tray of cell was completely covered with mud or sand and silver chloride to the water. The zinc disk has subjected to a pressure comparable to a depth of six small holes to allow water to circulate under 50 feet. In these tests, the effect of the mud and the cell. A threaded bakelite boss or nut is se sand upon the delay time was negligible, indicat cured in the center of the disk for holding the ing that, in this respect, the arming cell is su arming cell on the threaded piston rod of the clock perior to a soluble washer. starter. The cell is not suited for use on extenders be When the delay-arming cell is immersed in sea cause the larger diaphragm area of extenders in water, a primary electric cell generating an creases the total thrust on the cell and breaks the E. M. F. of about 1 volt is formed; the sea water cell at lower pressures. In the case of extenders is the electrolyte, the zinc disk is the anode, and Mark 12 Mods. 3 and 4 the situation is particularly the silver chloride is the cathode. The resistor unfavorable because pressures not sufficient to completes the circuit and limits the current break the cell may cause deformation of the disk through the cell. The time required for the zinc sufficient to permit arming. It may be used on plate to deteriorate and release the piston rod de extenders Mark 14 Mods. 1, 2, 5, and 6 in place of pends basically on the cell current and thickness a short-time soluble washer to prevent operation of the zinc disk. of the extender by impact when the mine strikes 'rhe delay time of the cell is affected by the pres the water as it is planted. Since the effective area sure, salinity, and temperature of the water around of the extender diaphragm is 4 square inches, and the cell. Water pressure, acting on the diaphragm that of the clock starter diaphragm is 1.2 square of the clock starter, exerts a thrust on the zinc disk. inches, the delay period for the cell used on these The effect of pressure for a temperature of 75° extenders may be estimated by multiplying the F. and a salinity of 30 parts in 1,000 is shown actual depth by 3% and proceeding as though the in the graph. A pressure of about 240 pounds device were a clock starter at this calculated depth. per square inch (540 feet of sea water) on the Until further tests have been made, however, it is diaphragm of a clock starter will break the zinc recommended that delayed operation not be relied disk at once. The effect of salinity variations upon when the cell is used on a Mftrk 14-type, between 15 parts per 1.000 and 30 parts per 1.000 is extender. very small, but below 15 parts per 1,000 the delay time of the cell increases rapidly, and the cell can not be used in water of lower salinity than 10 parts per 1,000, or in fresh water. The salinity of sea water is commonly 30 parts per 1.000. A change of water temperature of 10° F. changes the delay time inversely by approximately 15 percent. To estimate the delay time of the cell in a prac tical case, consult the graph for the time delay at 75° F. for the depth in question. If the tempera ture is not 75° F.. increase the time by 15 percent of this value for each 10° below 75° and decrease it by the same amount for each 10° above 75°. The delay time should then be accurate to ±1 day. DEPTH OF WATER IN FEET Countermine shock and the impact of planting EFFECT OF DEPTH U/’O.V TIME • are not expected to affect the arming cell Mark 2 Mod 0. Severe vibration and shocks producing Temperature, 75° F. Salinity, 30. Zinc disk, 0.016 accelerations up to 1,000 g. have not damaged it. inch thick. Resistor, 200 ohms. CONFIDENTIAL 29 The failure of a wet parachute, when the mine EFFECTS OF WATER is laimched at standard speeds of 200 or 210 knots, is due principally to the abnormally high forces ON PARACHUTES on the fabric caused by the zero air permeability. Failure is also partially due to the loss in strength UESTIONS frequently arise as to the effects of the material, but tests indicate that this alone is Qof water on the operating reliability of the not sufficient to cause a high percentage of failures parachutes used on United States Navy mines, and at standard laying speeds. tests have been made to determine these effects in Tests made on completely wet parachutes, terms of launching conditions. installed on Mark 25 mines, to determine the These tests indicate that water has two effects maximum launching speeds have shown that the which cause failure of the parachute material. parachute Mark 2 (6-foot) will operate satis First, the strength of the material of the parachute factorily at 130 knots or less. Parachutes Mark 3 is reduced to 40-45 percent. Secondly, the air Mods. 2, 3. and 4 (9-foot) can be launched at 120 permeability or porosity of the material (200 to knots or less. These launching speeds are the H 300 cubic feet of air per square foot of cloth per maximum recommended speeds for wet parachutes, minute for a dry parachute) is reduced to practi and occasional failures may still occur. It is noted cally zero. This later effect can be illustrated that at these slower launching speeds the opening \ by throwing water on a window screen; the time of the parachutes is variable, and may amount small holes in the screen are closed by a film of to approximately twice as long as the opening time water and flow of air through the screen is at higher speeds. The result is a greater dispersion restricted. of mines. 30 CONFIDENTIAL The above tests were concerned only with com pletely wet parachutes. However, other tests were made with parachutes which had been exposed to high relative humidities. The results of these tests show that no appreciable reduction in air perme ability of the parachutes occurs, but there is a 35- to 40-pei'cent loss in strength of the material. As mentioned above, this loss in strength usually does not result in parachute failure when the mines are launched under standard conditions. Current assembly instructions indicate that parachutes should not be removed from their waterproof containers prior to use, as they are sus ceptible to fungus growth and the material is often destroyed by rotting. Field activities should not attempt to dry out parachutes, because tempera tures of more than 150° F. will injure the sheer rayon fabric and lower temperatures accelerate the formation of mold and fungus growth in packed parachutes. Parachutes which have be come damp should be discarded. NOMOGRAPHS OF MINE TRAJECTORY DATA Illustrated at left are nomographs of no-wind range and drift which have been constructed from experimental data obtained from actual mine drops. These nomographs will be of use in making quick estimates of mine flight characteristics. CONFIDENTIAL 31 MINE DISPOSAL 4 operations, been ing duties ting to ing minefield believed success tegral mine into Blimps gun only LTA were fact However, — 32 15). It guide OR operated the of USE MINE NAVY with mines danger that employed was destroyed disposal officers, for were a enemy part Key in Although were short that sweepers originally and an in during this spotting that limited notably West of with areas. one average for also minefields OF the period to duties unusual a in by BLIMP DISPOSAL 7-day the were surface prevent minesweepers minefield question an connection on the used LT for intended At and in first last of operational while their airship's A operating a the mission the Key 31 and in November task time shipping craft photographic menace arose rounds the most first (Mine functioning Mediterranean, the West, to with FOR unit. a 50-caliber European engaged employ is charting pass have blimp part as conference period M attested per to minesweeping from however, a to arfare through Navy The to navigation. mine. whether previously performed the as the purposes. in 22 of straying machine theater blimps by blimp an clear Notes drift blimp mines spot their with it the the in or is existing surface not steady before distidct of current, rough beyond It basis the ment. (4) speeds: appeared a LTA ability blimp of seas: platform in the with advantages these records and officers conjunction (3) to could visual (2) that machine heavy destroy ability advantages with maneuverability of the effectively the range over this seas, blimp good to ‘ blimp mines gun with cover the of having and might visibility undertook fire. small destroy mine surface which, would large CONFIDENTIAL the been and There otherwise disposal craft. enthusiasm areas regardless mines due have craft: wide the attempted were to quickly; On several experi on range craft. wind, (1) drift the the no of of a blimp took station as nearly as possible over the MINE center of the echelon. The mine disposal craft were deployed along the flanks. When a mine was DISPOSAL cut, the sweeper reported it to the OTC who in turn assigned the blimp or one of the small craft to the task of disposal. The blimp maneuvered into position with engines idling, usually firing down wind. The machine gun was located in the top of the gondola just above the pilot, affording the gunner an unobstructed view. One or two short bursts were generally sufficient, especially in rough weather when the lapping waves would quickly fill the case. On calm days it was neces sary to pierce the mine very close to the water line. The blimp would linger until certain that the mine was sinking and then move on to her next assignment. The blimp functioned very effectively as a mine disposal craft. The Task Unit commander also believed that it would serve a useful purpose as an observation point from which to direct the mine-disposal operations, since it afforded such a good view of the area. However, no attempts was made to put this idea to a test as the blimp was unable to remain with the Task Unit for a long enough time. Since no mines detonated as a result of the blimp’s fire, it was impossible to determine whether or not the safety margins of altitude and approach would have been sufficient to provide adequate protection from the blast impact of a mine explosion. For that reason the facts per taining to the blimp’s suitability for this type of duty are somewhat inconclusive. Howevfer, as observed under the conditions existing during the Key West operation, the blimp was as success ful as the surface craft at mine disposal, and, in For several days prior to the blimp’s appearance rough weather, much faster and more efficient. at the scene of operations, the pilot accompanied the Task Unit Commander into the minefield to study existing methods of mine disposal and fa FLOATING MINES miliarize himself with the communication pro cedure. The Mine Disposal officer discussed the. OFF THE WEST COAST Mark 6 mine in detail, with special emphasis on In recent weeks, there have been numerous the safety factors affecting the blimp’s altitude reports of floating mines off the West coast of the and approach. As several swept mines had deto United States. In one area, as many as seven nated on the surface while under fire, it was de were reported within a period of 10 days. The cided that a distance of 500 yards and an altitude most likely explanation for their presence jn of 300 feet would provide an adequate margin of United States waters is that they broke loose from safety and at the same time permit a sufficiently Japanese defensive minefields and were carried by close approach for accurate fire. currents across the Pacific. Most of the mines As soon as the sweepers entered the field, the sighted or recovered were covered with sea growth, CONFIDENTIAL 33 MINE DISPOSAL indicating of cases, nationality considerable beaches posal out description the rendered charge show indicating (Mine who Circ. new their I). School. uates AM (MD). dered transferred 5 ing refresher loads mation. resentative Mine manding meets the tional load 34 Positive In them During in Prior C.. mines by ’ actual off designators s are Ltr. order Norfolk but rating, Officer. more DESIGNATORS NEW of TRANSFER TO Warfare Depot depth gun to attached which the will the enlisted are from Washington. and the to safe trained it report 81-45 training sighted that The officers the PACIFIC and readily that, overhaul identification that ships following and is Japanese. reporting ammunition period have BD to while of charges Bomb definitely Thirteenth in was several considered the for past ships they type duty Notes personnel ( Yorktown, Commander the also to to have OR NDB. like in at the very general East general off graduates their of of OF Disposal Commander the 6 records had has bomb then within the in DUTY detonated and MD mines months, D. been -I time. personnel. designator the to facts: the — sensitive This 31 coast, MINESWEEPERS the Atlantic identified special 15. been dock Norfolk, been Naval probable C.. and proceed of coast projector are March. overhaul JB. instructions or established p. where Pacific. the found of supposition will School. of (u) these Service impossible put 2(>) mine each in several and fuel enlisted qualifications, they the navy answered District, when to Service the Fleet The to 45-314). be ; (BD) on the an that them on gunfire. gives (&) Mine division charges of disposal mines Norfolk and identified Washington. water contained board Before yard. advance West fired division divisions Squadron Mine by vessels nearly several and have personnel Squadron added in is Disposal recently as the to the BuPers as many borne Grad for so upon, coast at JB infor to is Dis Addi shov begin may been com two JB rep all that and to un of the by or un a to ’ of a s 5 all availability. conference ual teams cers fire publications, up and sweeping refresher sage. cers they ther and While hands as Before men fighting, coordinate of 2 1 2 1 1 1 2 are Commander follows assignment. attend report streamed, Measured and magnetic as minesweeping sweeping as cises the casualties formation simulated radio), drone). out are day days: readiness day: by days: day: day get Then days: the A. can P. briefed A. officers P. a OTC training. sweepers leaving is conducted : Commander speed M. M. of division towed. ashore from : M. ships and M. get consist to CIC Gunnery : and Degaussing held Underway — Overnight — upon — Alongside — formation the simulated and Commander RDF leave Magnetic at any mile of on officer Fueling for Exercises range assault a to curves, and (by are Minecraft, effective training details between Kent Norfolk, tanker Service the and what with of actually This departure. other gear gear, during calibration outside in visual exercises calibration ASW maneuvers as Service the off Island Service sweep the sweep. calibration to the of adjustment for with (and and training compass at specialties necessitating and observer. in Squadron the letters at operations expect in the (. yard. the the school, signals Pacific division reaching ’ of anti-aircraft sea departure ape regrouping, Chief. CONFIDENTIAL to towing and formation sometimes off commanding Squadron (surface, 4 10-day Cape commanding These of Squadron to a (if Pacific Annapolis. exercises, are during Charles and compensation. is 6 pitometer YMS. and without Fleet at and desired. 5 weeks These Pacific usually commander of equipped). Charles. and underway the to Wolf obtained, and operations tactics dropping individ inspection sleeve by charts, exercises outline 5 moored the actual) for firing, mine Pacific and yard mine 5 City. exer being voice gear offi Fleet Trap both pas log set fur and offi A and in a MAGNET COILS FOR MK. 6 sweep wires are recovered until the otters are in MINESWEEPING a position near the stern fairleader blocks. The AUXILIARY CONTROLLERS davit whip hooks are connected to the otter strong backs as described above and the otters are two- The Bureau of Ships is cognizant of the inade blocked well clear of the water. The otters may quacy of the square wave holding magnet coils have to be lashed into the ship’s hull to prevent originally installed in Mark fi auxiliary control damage from violent pounding but they will be lers supplied 180-foot AM’s and YMS’s. These high enough out of the water to permit the vessel EQUIPMENT coils were designed by the manufacturer to operate to maneuver at high speeds. on a 50 percent duty cycle. Therefore, if a coil is energized more than half the total time of opera tion of the Mark 6 auxiliary controller, overheat CABLE FOR TOWING ing may result and insulation failure occur. In order to obviate this difficulty, the manufacturer A MARK 4 (v) GEAR ASTERN was requested to provide a magnet capable of The Bureau of Ships is supplying 4-conductor operating on a 100 percent duty cycle. Conse cable in 1,600-foot lengths for towing A Mark 4 quently, a new unit has been designed which con (v) gear astern. Stocks of this cable are being sists of a new core and two of the original coils shipped to the Navy Yard, Mare Island, and to connected in series. These new magnets are now the Spare Parts Distribution Centers at Guam, in production and have been installed in controllers Manus, and Pearl for issue to minesweepers. This recently shipped. Coils for all 250-volt Mark 6 cable is for specialized application against acoustic auxiliary controllers are being distributed to mines of certain sensitivities, and is to be employed the vessels by the Bureau of Ships. Additional operationally only in accordance with sweeping stocks are being shipped to the Spare Parts Dis instructions to be issued when use of the gear is tribution Centers. specifically directed by cognizant commands. AUXILIARY STERN DAVITS SHORE SPARES AND FOR 180-F00T AM’S SHIPS’ ALLOWANCES Vessels of the 180-foot AM class are fitted with Requisitions from ships and shore activities two removable auxiliary stern davits to facilitate requesting shore spares for magnetic minesweep streaming and recovery of O-type minesweeping ing generators and control equipment to fill ships’ gear. These davits permit placing the otters in allowances are frequently received in the Bureau. a ready position at the stern some time prior to the Data on shore spares as contained in the pertinent actual command to stream gear and also serve machinery allowance lists are included only for as a hanging position for the otters during tem information and should not be construed as au porary recovery of the gear. thority to carry the items on board ship. When When the otter is to be placed in a ready posi an item designated as a shore spare is required for tion at the stern for streaming, it is picked up by immediate installation in a ship in an advance the crane from its stowage rack on the fantail and area, it should be requisitioned from the nearest swung outboard to an auxiliary davit. The davit Spare Parts Distribution Center or local spare whip hook is connected to an eye on the otter parts activity. For ships operating in continental strongback, or to the strongback itself, and the waters, the material should be requested from the otter is shifted from the crane to the davit by Bureau of Ships. All shore spares which may now taking a strain on the davit whip and easing off on be aboard ships should be forwarded to the nearest the crane whip. The otter is two-blocked at the Spare Parts Distribution Center or local spare davit head well clear of the water. The crane is parts activity. When a shore spare is used for then trained to a position over the float stowage immediate replacement, the defective item re preparatory to streaming. moved from the ship should be forwarded to the When it is desired to recover the gear tem nearest Spare Parts Distribution Center or local porarily. without stowing the otters on deck, the spare parts activity for repair if repair is feasible. CONFIDENTIAL 35 MISCELLANEOUS tri bells shipped were trollers) NObs-410 distributed of a burg. remains NObs-410 furnished gates 180-foot 36 (620)-C-FN12S Is- The set A 4 Special long May originally of from DIESEL GE recent A DEPRESSORS instructions for majority the to AM's MARK ax to installed 1945. SPECIAL the further and Service Mechanicsburg, the (used to tce'rt here, exciters. he Bureau Bureau requiring GENERATOR some BuSliips shipped Naval of A 2 distributed. A2- -short ix with for distribution. copy in General Diesel-generators GEAR trilling SERVICE vessels, !1 FOR of of VMS's the Supply Subsequent without of of Mark letter the Ships pnrarant Ships streaming each — Motors-General referring 11 covers but why and S8 Depot. May These 6 (Code covers request letter 1-1-(3) All a I auxiliary y. not? quantity 45). arrangement on covers to VMS's 660m). Mechanics on are 1 should (C-S81 1 Contract Contract < the promul (660m) nek request being Elec- AM's were con still and end r*on, be 9 gear, and boom Loom pressors A at weights sels Norfolk Mark astern, box Distribution merge Depressors (i. which » Depressors an Mark Aek'netieledynient No. No. Nn. No. No. No. e.. Mint No. No. No. No. No. No. Naw V use or because .Mint eration* Detail Activity adequate vv forward when ami 6 2 4 5 1 IO 2 21 1 13 depot ACKNOWLEDGMENT 2S 2* UB a the YMS 1 iwtnbhi the #137 si of . gear the previously dtlnit ship's 2 ...... and -’ . are s depressor Report* fantail. special (c). gear are .. the for vessels standard the । Centers on | । 1 । used Mare Lt. are Lt. Lt. Lt. Lt. Lt. Lt. Lt. on Lt. Lt. Lt. Lt. Lt. Lt. Lt. Lt. Lt. Lt. Capt. Lt. Lt. Lt. Lt. Lt. Lt. depth I allowance) . not and • the gear such O. Comdr. E. do (Jg) (ig> (j«) M. AM Received of depressors . being T. T: G. L...... T. T. T. L. T. T. T. T. W. E. 11. Submitted B. Period supplied. in J. R. being N. ... a N. N. are N.D. When ND. . N.D. \ Mine . Island permits A Osteen Seward Seward Seward Seward Seward Seward Atkins Seward Anger. Seward Seward R. when Ehrlich Iv.-k Prado at Brown is M. vessels M. suitable and 1). D. 1> E. Swinburne place Mark streamlined capable. Gage Pearl. streamed C. Blait Blair Blair Blair Blair Blair Levinson Assembly shipped method by provided (3) 10 (3) (LM. (7) (4) Jones . DMS A by- to streamed . and G5) (7) (2) the 3 . . May the Mark with is 2 OF of the . depth Use Manus, CONFIDENTIAL Chief (f) front vessels. gear the the to of Depot REPORTS Navy from in A 2 of for 1 । 10 (high 1 written of weights 5-20-15 5-22-45 4-20-45 5-21-45 4-24-45 gear 5-28-45 5-23-45 5-11-45 5-10-45 5- 5- 5-30-45 abeam. 5-20-45 streaming 4-22-45 4-27-45 4-IO-45 4-27-45 4-20-45 4-20-45 5- 5-12-45 5-11-45 5-16-45 5-15-45 Spare Mark 5-16-45 4-12-45 4-25-45 • • '• at Date sets the to streamlined 22 13 June _i> 8-45 the 7-45 and 2-45 3-45 Naval 1 and YMS 15 a speeds Yards be i 15 ; ’ ’ The is hammer , . 1 . i i i Dale of special speed) special ceived 0-10-45 5-10-45 5-29-45 6- 5-23-45 5-23-45 6- 5 6-12-45 6- <, 5-23-45 6-12-45 6- 5-2S-45 Mine Guam. 5-25-45 5-14-45 2 5-20-45 5-11-45 6 5-30-45 5-25-45 5-30-45 6-10-45 6- 6- 6- 5-25-45 5-26-45 5-21-45 5-30-45 towed IPJ/o towed — 28 Parts Op 6-45 4-45 8-45 4-45 s । 1 (a). 1-15 1-45 1-45 -45 sub re ves two — 45 de ; 45 1 ~ ’ at of A BUREAU OF ORDNANCE PUBLICATION ON MINES AND MINING The following are additions and corrections to Cover dale No. Title and date of Classification the list of Bureau of Ordnance Publications con ______I last revision tained in Mine Warfare Notes 4-45: 942 . . Mine Firing Mechanisms A -5 15 May 45 . Secret. OP’S AND ORD’S Mod. 0 and A-5 Mod. 1- Description and Instructions OP HIS—Add to title: (Change -I—12 April for Testing. Mine Mark 25 Mod. 2—Descrip |1 Feb 45 ... 1945.) 943 Confidential. tions and Instructions for [15 Apr 45.... » Assembly and Testing. | Adil to Inf: 944.. Mine Mark 25 Mod. ^.Opera 1 Apr45 .. Secret. tional Characteristics. OP-1394. Bombing Table for 2,000-pound I Feb. 45... Restricted. 045...... Mine Firing Mechanism A-6 5 May 45 ... Secret. Aircraft-Laid Mine Mark 25 Mod. 0—Description and In Mod. 0. st ruct ions for Test ing. OP-1395 Bombing Table for 1.000-pound 12 Feb.45.. Restricted. 949 Mines (Practice) Mark 41 Mods, 15 May 45... I'onfldentia] Aircraft-Laid Mines AX Mark o, 1. and 2-Description and 26 Mod. 1 and Mark 36Mods. 0 1 n st ruct ions for Use. and 1. OP-1459.. Bombing Table fro 2.000-pound 22 Mar. 45. Restricted. Aircraft-Laid Mines Mark 25 BUORD MULTIADDEE LETTERS Mods. L 2, and 3. Add to list: OCL’S S 7 6- 1 Mines- Instructions for Modify 30 Apr. 45... Restricted. (Re6b). ing Mark 1 Type Clock Start Add to list: ers and Mark 12 and 14 Type* Extenders of. to Reduce Gal M6-45 . Mines—Clock Starters Mark 1 i 1 Max 15 Restricted. vanic Corrosion. Mods. 1 and 2. NOLR’S The followhiej list supersedes the list of NOER's DISTRIBUTION LIST MINE WARFARE NOTES 5-45 printed in Mine Warfare Aotes 4-4$: List 1.-—a (3 copies to Cint 'I’ac. CinCLant) ; b, <• (2 copies to ConiFleetAirs) ; <1, e, f, g, h, Cover date No. Title and date of Classification i.j.k.l. last revision List 2.—a (8l (Fleet AirWings only) ; f, g, I. n (nil copies via air mail); q, u. 774 Mine Mark IS—Operational Nov. 43 Confidential. List 3—it, <1. li. i, j, w, w-1, x, y, y-1, z, z-l, Characteristics. aa. bb. ii, jj. kk. mtn, pp. 782 (1st Mine Mark 25—Description and 1 July 44 Restricted. rev.). Instructions for Assembly. List E-3.—(2 copies) (all copies via air Handling and Planting. mail). Mine Mark 13 Mod. 5 (A-3 Mod. fl Jan 44 . |confideniial. List 4.—a, <1, i. j. w, x, y. z. aa. bb, ii. jj. kk, 1 Conversion Kit) Description (is Aug. 44 . and Instructions for Use. mm. pp. 859 (1st Mine Mark 25—Operational 1 May 44 .. j Confidential. List 0.—a. rev.). Characteristics. [15 Oct 44 Lisi 7.—a (l).b. f, g. It. s, x, z. 878 Field Mine Test Sets- Inst ruc May 45 I Confidential Lisi S.— f.j, cc.ee. tions for Using. List 10.—t <2 copies each, except Com 902. Part Mine Accessories. Description 15 Feb 45. Restricted. I and and Instructions for Testing. mander Northern Group—1 copies; Command Part II. er Patrol Forces. Inshore Patrol, Eighth Naval 915 Instruct ions for Installing British Oct 44 . i Restricted. District—10 copies; and Commander Naval 44-Day Clock in U. S. Naval Local Defense Forces Twelfth Naval Dis Mines. trict—S copies) ; jj, mi. (2 copies) ; u. 938 . CD-14 Delayed Arming and 1 May 45 . Confidential. List 14.—a (25 copies). Sterilizing Clocks for Mines— Senior Member. Minesweeping Tria) Boards, Forw ard ing ( »f Inst rucl ions Pertaining to. C/0 Comdls.. Naval Districts 1, 3. 4. 5, 6, 7, 8, 948 Mine (Practice) Mark 40 Mod. Restricted. 11. 12, 13. 1 0—Description and Instructions Dp-30-3M Special Distribution List No. 1 for Use of. (District Minecraft). 956 . Conversion Kits Mark 9 Mod. 0 if 15 Dec44 .. ^Confidential. and Mark 10 Mod. 0—Descrip 1-5 Apr 45 Op-30-3M Special Distribution List No. 2 tion and Instructions for Use. (Mine Disposal Units). 869 ...... Mines Mark 12 Mods. 3 and 4— 15 Dec 44... Confidential. Op-3o-3M Special Distribution List No. 3 Descriptions and Instructions (Special Degaussing activities). for assembly. Op-30-3M Special Distribution List No. 4 940 Mine Mark 25 Mod. 1—Descrip 1 Apr 45. .. Confidential. tions and Instructions for (Special Activities). | Assembling and Testing. CONFTDENTIAL 37 This command is of the opinion that a minefield is best swept in laps perpendicular to the axis of the line of mines. An attack parallel to the line can only result in sweepers frequently and simul taneously encountering a large number of mines and if obstructors and snag-lines are present, in the resultant confusion some sweeper is bound to find himself not only in unswept water but still heading into the minefield. Even if the mines are cut clearly and without undue drag on the gear, then a profusion of “Floaters” will ensue to menace the formation . . . ONO Comment: See FTP dOJ^A, paragraph '.load. In several operations sweeping has been slowed and sweepers endangered by the great 'number of floaters cut in a single pass. As many as 7!) mines have been cut in 1 pass by a. single sweeper formation. The following excerpts hare been selected from, various recent minesweeping reports because of their general interest, or to illustrate the prac tical application of established sweeping methods. Better doctrine is needed for employment of markers and dan buoys. Their use should be re duced to a minimum and they should be sunk or recovered by minecraft when swept or of no fur ther value. Buoys adrift almost always result in alarm in the belief they are mines. While care should be exercised not to destroy markers serving Mines visible from AM vessels in conducting a useful purpose, any vessel sighting a real mine on sweep appeared to be moored at depths of G to 9 the surface should invariably make every effort feet in water 15 to 20 fathoms deep with possi consistent with its mission to sink it. There is a bility of shallower plants in shallower water. It tendency for ships sighting suspicious objects in is also recommended that area be dragged before the water to report the location and depart the use as an anchorage to remove any plants deeper area, leaving minecraft the difficult task of relo than the 60-foot sweep. Sweeping operations cating and disposing of the item, whatever it were limited to GO-foot depth in area because of might be. Single aimed 40-mm. shots are effec limiting depth of water in northwest and south tive in disposing of mines . . . west courses of field. It is considered that, this minefield as planted was extremely effective against surface vessels of all types. The extent of the field and disposition of mines in rows was not readily apparent until * It is recommended that organized aerial mine entire field was covered. Mines were planted in spotting be made a part of future minesweeping short rows staggered across field at irregular operations in the Pacific, the sole mission of air intervals . . . craft assigned for this purpose to be the search for and location of enemy minefields. It is believed CXO Comment: Where complete coverage that the organized operational use of aircraft for with “O'' type minesweeping gear cannot be mine spotting in conjunction with minesweeping obtained due to restricted maneuvering room, operations will be of great value in bypassing or varying depths, or other causes, a bottom drag sweeping of enemy minefields during amphibious is recommended. operations. This has been proved in the Mediter 38 CONFIDENTIAL ranean where aerial mine spotting was success tilla’s navigating officer made an air reconnais MISCELLANEOUS fully used to assist minesweepers off the coast of sance in a Walrus of the area to be searched before Italy and the southern coast of France. The the operations commenced. Numerous conical search for mines should be the sole mission of floats were observed; some on the surface. The slow-flying aircraft equipped to provide photo position of the watching floats was then fixed by graphs of areas where smoke market's are an M/L. The Walrus further cooperated by dropped . . . dropping smoke floats indicating the extremity of the mine lines. The assistance of this air spot ting was so valuable that the area Fighter Wing was approached and further air spotting assist ance was arranged for all subsequent opera The following excerpts are from British tions . . . sources: THE "TAIL” OF THE DOG THAT BIT HIM! An echo of the spirited action of three BYM’s without asdic or depth charges, on the 26th of Aircraft on patrol reported seeing a large num December last, in sinking two Midget submarines ber of mines 5 miles North of Cherbourg on the is now revealed in an official report. When the. 28th in the vicinity of a declared dangerous area. three ships were sweeping LL/SA in Q forma Next day another air patrol reported 20 mines 5 tion, a submarine was reported by BYMS (A) to miles NNW of Le Treport. So far this area has port and at the same time BYMS (B) reported a been unexplored by minesweepers and is likely to periscope to starboard. BYMS (C) and (A) be heavily mined. At the request of A. C. Dover, immediately gave chase to the Midget on their a dangerous area (QZX 1536) was then declared port side and BYMS (B) turned to starboard in within a circle of 2^ mile radius. This is another attempt to ram his bird. The port side Midget example of the value of aircraft cooperation in started to zig-zag and an attempt to ram by the spotting mines although, in this particular case, BYMS (C) glanced off. BYMS (A) rammed there is some suspicion that the reported mines but the submarine continued on its way. BYMS may turn out to be boom-defense buoys ... (C) then turned to ram again and opened fire with Oerlikon and small arms with repeated hits. The submarine then stopped and remained on the surface. To make sure of his prize, BYMS (C) o then proceeded to take a turn round the sub The minesweeping forces in the Firth of Forth marine with his LL cable, which caught the con were provided with a cheer this week in detonat ning tower in the bight. BYMS (C) was then ing a groundmine on the 3d, 3% miles East of the able to bring the Midget under his stern by haul Bass Rock Light during routine sweeping. The ing in his LL tail. Wires were made fast to the mine is thought to be of an old lay probably of submarine in an attempt to take her in tow but November IDJfl vintage . . . the towing wires parted as the submarine foun dered. The starboard Midget began to zig-zag at 5 knots, but when BYMS (B) was one cable off, the conning tower hatch opened and a German was seen frantically waving his arms. The BYMS struck the Midget just forward of the con ning tower and she passed under the bow of the minesweeper and reappeared on the other side to finally sink. The one survivor clung to the LL tail and was taken prisoner . . . SUCCESS OF AERIAL MINESPOTTING Preceding the operations of the 12th MSF in clearing a channel Piombino to Leghorn, the Flo CONFIDENTIAL 39 ASSEMBLY AND PLANTING OF MK. 25 MOD. 0 DRILL MINE At the completion of the course in Mine Assem loaded on a laying barge, equipped with a re bly anti Test at the Naval Mine Warfare School, covery line and a marker buoy, and launched. several drill plants are conducted by the students. After the arming time has elapsed, the laying I'he purpose of these drills is to test the student s barge is used to sweep the mines which are located ability to prepare mines for planting and to give by the marker buoys. Firing of the mine is indi him visual evidence of his accomplishment under cated by the surfacing of the indicator float which somewhat realistic conditions. is released from the mine when the operation of the The photographs illustrate certain phases of the mine mechanism fires the primer in the release procedure followed in the drill plants of magnetic pistol. Following firing (or failure to fire) the mines. One mine is assigned to a group of about mine is recovered by means of the recovery line four students who completely assemble and test attached to the marker buoy, washed down with it in tin- laboratory and install the firing indicator fresh water, and disassembled in preparation for float with its release pistol. The mines are then the following plant. 40 CONFIDENTIAL U S. GOVERNMENT PRINTINS OFFICE 1945 These NOTES can be of maximum service only if operating personnel freely contribute items of interest. Accordingly, contributions are invited, and mav be addressed directly to the Director, Base Maintenance Division, Mine Warfare Section, Naval Operations, Navy Department, Washington D. C., with a copy to immediate Cummanu*. j Officer Contributions of all types are welccm (. omments on articles which have appeared s for the improvement of equipment or techniqu■ t ;.id peis< i )unts of operations Clear photographs or negatives to accompxaj the se