WAR DEPARTMENT iENGINEER FIELD MANUAL Volume II MILITARY ENGINEERING (TENTA TI VE) PART TWO DEFENSIVE MEASURES U S. Army PlWilar HWsforv Instiljfe ENGINEER FIELD MANUAL VOLUME II MILITARY ENGINEERING (Tentative) PART TWO DEFENSIVE MEASURES PREPARED UNDER THE DIRECTION OF THE CHIEF OF ENGINEERS UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON: 1932 For sale by the Superintendent of Documents, Washington, D. G. Price 30 cents PIOEEWTY OF US ARMY WAR DEPARTMENT, WASHINGTON, June 25, 1932. Part Two, Defensive Measures, Engineer Field Manual, Vol- ume II, Military Engineering (Tentative), is published for the information and guidance of all concerned. [A. G. 062.11 (7-19-30).] BY ORDER OF THE SEORUMARY OF WAR: DOUGLAS MAcARTHUR, General, Chief of Staff. OFFICIAL: C. H. BRIDGES, Major General, The Adjutant General. LIST OF FIELD MANUALS A MANUAL FOR COMMANDERS OF LARGE UNITS. (M. C. L. U.) Vol. I. Operations.-A guide for commanders and staffs for tactical operations of large units. II. Administration.-A guide for the administration of large units in a theater of operations. STAFF OFFICERS' FIELD MANUAL. (S. O. F. M.) Staff principles and functions applicable to the staffs of all units, together with pertinent reference data. BASIC FIELD MANUALS. (B. F. M.) Training, administrative, and reference data applicable to more than one arm, with special reference to the smaller units. Vol. I. Field Service Pocketbook. (F. S. P.)-The individual. II. Infantry Drill Regulations. (I. D. R.)-Drill, dismounted ceremonies, and inspections; the infantry pack, display of equipment, and tent drill. III. Basic Weapons. (B. W.)-Marksmanship and mechanical training of the rifle, automatic rifle, pistol, machine gun, 37-mm. gun, 3-inch trench mortar, bayonet and grenade instruction. Technique of fire (37-mm. gun, 3-inch trench mortar, and machine gun) ; musketry and combat practice of small units, instruments. IV. Signal Communication. (S. C.)-Signal regulations and technical information needed by officers and enlisted men on signal communication duty of arms other than the Signal Corps. V. Transport. (T.)-Equitation, training remounts, use and care of animals and of animal-drawn, pack, motor and tractor transport. VI. Administrative Regulations. (A. R.)-Army Regulations essential to small units. VII. Military Law. (M. L.)-The Manual for Courts-Martial, including the Articles of War; the Rules of Land Warfare, including recent conventions relative to the sick and wounded of armies in the field and to prisoners of war; an epitome of the legal principles applicable to military forces when aiding the civil power. VIII. Operations of Combined Arms (Small Units). (O. C. A.)- The principles, doctrines, and methods governing the tacti- cal employment of combined arms with reference to the small units. III IV LIST OF FIELD MANUALS FIELD MANUALS FOR THE ARMS The manual for each arm contains, primarily, the principles, doctrines, and methods governing the employment of that arm and pertinent reference data. Infantry Field Manual. (I. F. M.) Vol. I. Units other than Tanks. II. Tank Units. Cavalry Field Manual. (C. F. M.) Field Artillery Field Manual. (F. A. F. M.) Vol. I. Organization and Drill. II., Tactics and Technique. Coast Artillery Field Manual. (C. A. F. M.) Vol. I. Harbor Defense, Railway and Tractor-drawn Units. II. Antiaircraft Artillery Units. Air Corps Field Manual. (A. C. F. M.) Engineer Field Manual. (E. F. M.) Vol. I. Engineer Troops. II. Military Engineering. Signal Corps Field Manual. (S. C. F. M.) Vol. I. Signal Corps Troops. II. Signal Corps Operations. TABLE OF CONTENTS CHAPTER 1. Camouflage: Paragraph Page SECTION I. General principles ---...-....-..- 1-6 1-3 II. Reconnaissance -----..-.- --------------------- 7-11 3-4 III. Construction ----------------------- 12-27 4-31 CHAPTER 2. Field fortifications: SECTION I. Principles of field fortification -..-.-.. .. 28-34 33-37 II. The effects of projectiles..............--.------- 35-41 39-40 III. Underground water and its relation to fieldworks__42-44 41-42 IV. Standard types of fieldworks....--.- 45-78 43-103 V. Protected shelters ...-------. - 79-145 105-172 CHAPTER 3. Explosives and demolitions: SECTION I. General principles ---------------....---------. 146-155 174-182 II. Demolition equipment -------------.------ 156-169 184-191 III. Methods of handling explosives --------...--- 170-201 192-221 IV. The demolition project...-------------..---------- 202-217 221-240 V. Mine warfare ..--....... - - - - - 218-227 241-244 FOREWORD Engineer Field Manual, Volume II, Military Engineering, is a compendium of technical information and suggestions as to the conduct of the most common operations undertaken by engi- neer troops in the theater of operations. The user of this manual should recognize that local conditions in the field will always profoundly affect the application of the principles and formulas given herein. The manual contains suggestions and guides to judgment rather than regulations to be rigidly adhered to. The manual will be published in three parts as follows: Part One, Communications: Chapter 1. Roads. 2. Bridges. 3. Military Railways. 4. Surveys and maps. (This chapter will be published when it becomes necessary to revise TM 2180-30 and 2180-37.) Part Two, Defensive Measures: Chapter 1. Camouflage. 2. Field Fortifications. 3. Explosives and Demolitions. Part Three, Construction and Utilities: Chapter 1. General Construction. 2 Water Supply. 3. Light and Power. vI ENGINEER FIELD MANUAL VOLUME II, MILITARY ENGINEERING (TENTATIVE) PART TWO DEFENSIVE MEASURES (The matter contained herein supersedes TB 195-20, December 20, 19287 (including Changes No. 1, January 2, 1931), TR 195-25, December 1, 1927, TR 195-30, May 15, 1926 (including Changes No. 1, January 2, 1929), and TR 195-40, June 15, 1926) Volume II supersedes the Engineer Field Manual, edition of 1918 (Profes- sional Papers of the Corps of Engineers, U. S. Army, No. 29) CHAPTER 1 CAMOUFLAGE Paragraph SECTION I. General principles_______ ___------------------- 1-- 6 II. Reconnaissance__-------------------------------- 7-11 In. Construction _-------------------------- 12-27 SECTION I GENERAL PRINCIPLES 1. Definition.-Camouflage is work done for the purpose of deceiving the enemy as to the existence, nature, or location of material, troops, or military works. The importance of camouflage depends in general upon the activity and effective- ness of the enemy's air service, although it is important to camouflage against ground observation. 2. Basic principle.-The basic principle of camouflage is de- ception. Deception is accomplished by suppressing all signs of abnormal activity near the object or deceiving the enemy as to the purpose of such activity; by making the object in- distinguishable from its surroundings; by making the object appear to be something else; or by complete concealment. 1 2 ENGINEER FIELD MANUAL 3. Hostile observation.-Hostile observation may be of two kinds, direct and indirect. Direct observation is by direct vision, aided or unaided by field glasses or telescopes. It is obtained from observation posts or aircraft. Indirect ob- servation, which is by far the most dangerous, is from the study of aerial photographs. 4. Patterns.-The pattern formed on aerial photographs by the features of the terrain influences to a large degree the measures taken toward deception or concealment. Patterns may be large and simple or intricate and confused. Detection by aerial photography is more difficult when an object is located in terrain showing a complex photographic pattern. Patterns are made by form, shadow, texture, and color. a. Form.--Form is the most important element. Regular forms quickly attract the eye, while irregular forms of human origin are lost in the irregular forms of the natural features. b. Shadow.-Shadow is what discloses form, and from the shadow theeperienced aerial photograph reader can visualize the object casting it. c. Texture.-Texture in camouflage is a quality opposed to smoothnf'0r polish and is illustrated by a rug of long nap. The nap is composed of innumerable fine hairs, each one when erect casting a shadow. When the rug is trod upon, the hairs are pressed down and texture is lost. When brushed, the hairs become erect and texture is regained. Substance with much surface texture absorbs light and photographs dark; if location in texture and surface reflects light, it photographs light. Grass or other vegetation possesses this property in a marked degree. The longer it is the darker it appears in the photographs, but when pressed down by the foot the amount of shadow is lessened, and it consequently appears lighter. Hence the obviousness from the air of a slight track or path:in grass which is quite inconspicuous from the ground. d. V_,---Color is the least important of the four elements that contribute to form patterns in the photograph, as it can be translated only into tones of black and white. Colors which may appear to the eye to match the locality do not match in photographs unless the texture of the material approximates the texture of the locality. Painted canvas or burlap of the same color as grass photographs much lighter on account of reflection due to lack of texture. ENGINEER FIELD MANUAL 3 5. Relative importance of camouflage requirements.-Field experience has shown that the relative importance of camouflage requirements is about as follows: a. Properchaieof position-40 per cent., b. Camouflage dis-cip in ftisrerp6tervance of camouflage reguibatrofs)-25 per cent. o. Proper erection of camouflage material-20 per cent. d. Camouflage material used-15 per cent. 6. Trpep Of 0d~Maget.-- ypes of camouflage include- a. Concealment, as by the use of screening to prevent direct observation of our activities. b. Variegated painting to deceive the observer as to the true pattern of what he sees. c. Fish nets hung with garlands of burlap or other material to cover batteries and other objects to make a blurred and in- conspicuous record on an aerial photograph. d. Road screens of natural or artificial material. e. Dummies which, though visible to the enemy, confuse and deceive him.