Brush work

1117. A fascine is a cylindrical bundle of brush, closely bound. The usual length is 18 ft. and the diam. 9 ins. when compressed. Lengths of 9 and 6 ft., which are sometimes used, are most conveniently obtained by sawing a standard fascine into 2 or 3 pieces. The weight of a fascine of partially seasoned material will average 140 lbs.

Fascines are made in a cradle which consists of five trestles. A trestle is made of two sticks about 6-1/2 ft. long and 3 ins. in diam, driven into the ground and lashed at the intersection as shown in Fig. 10. In making a cradle, plant the end trestles 16 ft. apart and parallel. Stretch a line from one to the other over the intersection, place the others 4 ft. apart and lash them so that each intersection comes fairly to the line.

To build a fascine, straight pieces of brush, 1 or 2 ins. at the butt, are laid on, the butts projecting at the end 1 ft. beyond the trestle. Leaves should be stripped and unruly branches cut off, or partially cut through, so that they will lie close. The larger straighter brush should be laid on the outside, butts alternating in direction, and smaller stuff in the center. The general object is to so dispose the brush as to make the fascine of uniform size, strength, and stiffness from end to end.

When the cradle is nearly filled, the fascine is compressed or choked by the fascine choker, Fig. 11, which consists of 2 bars 4 ft. long, joined at 18 ins. from the ends by a chain 4 ft. long. The chain is marked at 14 ins. each way from the middle by inserting a ring or special link. To use, two men standing on opposite sides pass the chain under the brush, place the short ends of the handles on top and pass the bars, short end first, across to each other. They then bear down on the long ends until the marks on the chain come together. Chokers may be improvised from sticks and rope or wire.

Binding will be done with a double turn of wire or tarred rope. It should be done in 12 places, 18 ins. apart, the end binders 3 ins. outside the end trestles. To bind a fascine will require 66 ft. of wire.

Improvised binders may be made from rods of live brush, hickory or hazel is the best. Place the butt under the foot and twist the rod to partially separate the fibers and make it flexible. A rod so prepared is called a withe. To use a withe, make a half turn and twist at the smaller end, Fig. 12; pass the withe around the brush and the large end through the eye. Draw taut and double the large end back, taking 2 half-hitches over its own standing part, Fig. 13.

When the fascine is choked and bound, saw the ends off square, 9 ins. outside the end binders. After a cradle is made, 4 men can make 1 fascine per hour, with wire binding. Withes require 1 man more.

A fascine revetment is made by placing the fascines as shown in Fig. 14. The use of headers and anchors is absolutely necessary in loose soils only, but they greatly strengthen the revetment in any case. A fascine revetment must always be crowned with sods or bags.



1118. In all brush weaving the following terms have been adopted and are convenient to use:

Randing.—Weaving a single rod in and out between pickets.

Slewing.—Weaving two or more rods together in the same way.

Pairing.—Carrying two rods together, crossing each other in and out at each picket.

Wattling.—A general term applied to the woven part of brush construction.

1119. A hurdle is a basket work made of brushwood. If made in pieces, the usual size is 2 ft. 9 ins. by 6 ft., though the width may be varied so that it will cover the desired height of slope.

A hurdle is made by describing on the ground an arc of a circle of 8 ft. radius and on the arc driving 10 pickets, 8 ins. apart, covering 6 ft. out to out, Fig. 15. Brush is then woven in and out and well compacted. The concave side of a hurdle should be placed next the earth. It wraps less than if made flat.

In weaving the hurdle, begin randing at the middle space at the bottom. Reaching the end, twist the rod as described for a withe, but at one point only, bend it around the end picket and work back. Start a second rod before the first one is quite out, slewing the two for a short distance. Hammer the wattling down snug on the pickets with a block of wood and continue until the top is reached. It improves the hurdle to finish the edges with two selected rods paired, Fig. 16. A pairing may be introduced in the middle, if desired, to give the hurdle extra endurance if it is to be used as a pavement or floor. If the hurdle is not to be used at once, or if it is to be transported, it must be sewed. The sewing is done with wire, twine, or withes at each end and in the middle, with stitches about 6 ins. long, as shown in Fig. 16. About 40 ft. of wire is required to sew one hurdle. No. 14 is about the right size, and a coil of 100 lbs. will sew 40 hurdles. Three men should make a hurdle in 2 hours, 2 wattling and the third preparing the rods.

1120. Continuous hurdle.—If conditions permit the revetment to be built in place, the hurdle is made continuous for considerable lengths. The pickets may be larger; they are driven farther apart, 12 or 18 ins., and the brush may be heavier. The construction is more rapid. The pickets are driven with a little more slant than is intended and must be anchored to the parapet. A line of poles with wire attached at intervals of 2 or 3 pickets will answer. The wires should be made fast to the pickets after the wattling is done. They will interfere with the wearing if fastened sooner. Two men should make 4 yds. of continuous hurdle of ordinary height in one hour.

1121. Brush revetment.—Pickets may be set as above described and the brush laid inside of them without weaving, being held in place by bringing the earth up with it. In this case the anchors must be fastened before the brush laying begins. The wires are not much in the way in this operation.

1122. Gabion making.—A gabion is a cylindrical basket with open ends, made of brush woven on pickets or stakes as described for hurdles. The usual size is 2 ft. outside diam. and 2 ft. 9 ins. height of wattling. On account of the sharp curvature somewhat better brush is required for gabions than will do for hurdles.

The gabion form, Fig. 17, is of wood, 21 ins. diam., with equidistant notches around the circumference, equal in number to the number of pickets to be used, usually 8 to 14, less if the brush is large and stiff, more if it is small and pliable. The notches should be of such depth that the pickets will project to 1 in. outside the circle. The pickets should be 1-1/4 to 1-3/4 ins. diam., 3 ft. 6 ins. long and sharpened, half at the small and half at the large end.

To make a gabion, the form is placed on the ground, level or nearly so, and the pickets are driven vertically in the notches, large and small ends down, alternately. The form is then raised a foot and held by placing a lashing around outside the pickets, tightened with a rack stick, Fig. 18. The wattling is randed or slewed from the form up. The form is then dropped down, the gabion inverted and the wattling completed. If the brush is small, uniform, and pliable, pairing will make a better wattling than randing. If not for immediate use, the gabion must be sewed as described for hurdles, the same quantity of wire being required.



The gabion, when wattled and sewed, is completed by cutting off the tops of the pickets 1 in. from the web, the bottom 3 ins., the latter sharpened after cutting, and driving a carrying picket through the middle of its length and a little on side of the axis. See that the middle of this picket is smooth. Three men should make a gabion in an hour.

Gabions may be made without the forms, but the work is slower and not so good. The circle is struck on the ground and the pickets driven at the proper points. The weaving is done from the ground up and the entire time of one man is required to keep the pickets in proper position.

If brush is scarce, gabions may be made with 6 ins. of wattling at each end, the middle left open. In filling, the open part may be lined with straw, grass, brush cuttings, or grain sacks, to keep the earth from running out.

1123. Gabion revetment.—The use of gabions in revetments is illustrated in Fig. 20. If more than two tiers are used, the separating fascines should be anchored back. Gabion revetments should be crowned with sods or bags.

The advantages of the gabion revetment are very great. It can be put in place without extra labor and faster and with less exposure than any other. It is self-supporting and gives cover from view and partial cover from fire quicker than any other form.

Several forms of gabions of other material than brush have been used. Sheet iron and iron and paper hoops are some of them. The iron splinters badly, is heavy, and has not given satisfaction. If any special materials are supplied the method of using them will, in view of the foregoing explanation, be obvious.

1124. Timber or pole revetment.—Poles too large for use in any other way may be cut to length and stood on end to form a revetment. The lower ends should be in a small trench and have a waling piece in front of them. There must also be a waling piece or cap at or near the top, anchored back. Fig. 21 shows this form.

1125. Miscellaneous revetments.—Any receptacles for earth which will make a stable, compact pile, as boxes, baskets, oil or other cans, may be used for a revetment. Barrels may be used for gabions. Canvas stretched behind pickets is well thought of in a foreign service. If the soil will make adobe, or sun-dried bricks, an excellent revetment may be made of them, but it will not stand wet weather.

Knots

1126. Square or reef knot, Fig. 22, commonly used for joining two ropes of the same size. The standing and running parts of each rope must pass through the loop of the other in the same direction, i. e., from above down ward or vice versa; otherwise a granny, is made, which is a useless knot that will not hold. The reef knot can be upset by taking one end of the rope and its standing part and pulling them in opposite directions. With dry rope a reef knot is as strong as the rope; with wet rope it slips before the rope breaks, while a double sheet bend is found to hold.



1127. Two half hitches, Fig. 23, especially useful for belaying, or making fast the end of a rope round its own standing part. The end may be lashed down or seized to the standing part with a piece of spun yarn; this adds to its security and prevents slipping.

This knot should never be used for hoisting a spar.



1128. Clove hitch, Fig. 24, generally used for fastening a rope at right angles to a spar or at the commencement of a lashing. If the end of the spar is free, the hitch is made by first forming two loops, as in Fig. 26, placing the right-hand loop over the other one and slipping the double loop (Fig. 27) over the end of the spar. If this can not be done, pass the end of the rope round the spar, bring it up to the right of the standing part, cross over the latter, make another turn round the spar, and bring up the end between the spar, the last turn, and the standing part, Fig. 25. When used for securing guys to sheer legs, etc., the knot should be made with a long end, which is formed into two half hitches round the standing part and secured to it with spun yarn.



1129. Timber hitch, Fig. 28, used for hauling and lifting spars. It can easily be loosed when the strain is taken off, but will not slip under a pull. When used for hauling spars, a half hitch is added near the end of the spar, Fig. 29.



1130. Bowline, Fig. 30, forms a loop that will not slip. Make loop with the standing part of the rope underneath, pass the end from below through the loop, over the part round the standing part of the rope, and then down through the loop c. The length of bight depends upon the purpose for which the knot is required.



1131. Bowline on a bight, Fig. 31. The first part is made like the above, with the double part of a rope; then the bight a is pulled through sufficiently to allow it to be bent past d and come up in the position shown. It makes a more comfortable sling for a man than a single bight.



1132. Sheep shank, Fig. 32, used for shortening a rope or to pass by a weak spot; a half hitch is taken with the standing parts around the bights.



1133. Short splice. To make a short splice, Figs. 33, 34, 35, unlay the strands of each rope for a convenient length. Bring the rope ends together so that each strand of one rope lies between the two consecutive strands of the other rope. Draw the strands of the first rope along the second and grasp with one hand. Then work a free strand of the second rope over the nearest strand of the first rope and under the second strand, working in a direction opposite to the twist of the rope. The same operation applied to all the strands will give the result shown by Fig. 34. The splicing may be continued in the same manner to any extent (Fig. 35) and the free ends of the strands may be cut off when desired. The splice may be neatly tapered by cutting out a few fibers from each strand each time it is passed through the rope. Rolling under a board or the foot will make the splice compact.



1134. Long splice (Figs. 36, 37).—Unlay the strands of each rope for a convenient length and bring together as for a short splice. Unlay to any desired length a strand, d, of one rope, laying in its place the nearest strand, a, of the other rope. Repeat the operation in the opposite direction with two other strands, c and f. Fig. 37 shows strands c and f secured by tying together. Strands b and e are shown secured by unlaying half of each for a suitable length and laying half of the other in place of the unlayed portions, the loose ends being passed through the rope. This splice is used when the rope is to run through a block. The diameter of the rope is not enlarged at the splice. The ends of the strands should not be trimmed off close until the splice has been thoroughly stretched by work.



1135. Eye splice (Figs. 38, 39, 40, 41).—Unlay a convenient length of rope. Pass one loose strand, a, under one strand of the rope, as shown in fig. 38, forming an eye of the proper size. Pass a second loose strand, b, under the strand of the rope next to the strand which secures a, Fig. 39. Pass the third strand, c, under the strand next to that which secures b, fig. 40. Draw all taut and continue and complete as for a short splice.



Lashings

1136. To lash a transom to an upright spar, Fig. 42, transom in front of upright.—A clove hitch is made round the upright a few inches below the transom. The lashing is brought under the transom, up in front of it, horizontally behind the upright, down in front of the transom, and back behind the upright at the level of the bottom of the transom and above the clove hitch. The following turns are kept outside the previous ones on one spar and inside on the other, not riding over the turns already made. Four turns or more are required. A couple of frapping turns are then taken between the spars, around the lashing, and the lashing is finished off either round one of the spars or any part of the lashing through which the rope can be passed. The final clove hitch should never be made around the spar on the side toward which the stress is to come, as it may jam and be difficult to remove. The lashing must be well beaten with handspike or pick handle to tighten it up. This is called a square shears are laid alongside of each other with their butts on the ground, lashing.



1137. Lashing for a pair of shears, Fig. 43.—The two spars for the points below where the lashing is to be resting on a skid. A clove hitch is made round one spar and the lashing taken loosely eight or nine times about the two spars above it without riding. A couple of frapping turns are then taken between the spars and the lashing is finished off with a clove hitch above the turns on one of the spars. The butts of the spars are then opened out and a sling passed over the fork, to which the block is hooked or lashed, and fore and back guys are made fast with clove hitches to the bottom and top spars, respectively, just above the each spar the distance from the butt to the center of the lashing. Lay two of the spars parallel to each other with an interval a little greater fork, Fig. 44.



1138. To lash three spars together as for a gin or tripod.—Mark on than the diameter. Rest their tips on a skid and lay the third spar between them with its butt in the opposite direction so that the marks on the three spars will be in line. Make a clove hitch on one of the outer spars below the lashing and take eight or nine loose turns around the three, as shown in Fig. 45. Take a couple of frapping turns between each pair of spars in succession and finish with a clove hitch on the central spar above the lashing. Pass a sling over the lashing and the tripod is ready for raising.



1139. Holdfasts.—To prepare a fastening in the ground for the attachment of guys or purchases, stout pickets are driven into the ground one behind the other, in the line of pull. The head of each picket except the last is secured by a lashing to the foot of the picket next behind, Fig. 46. The lashings are tightened by rack sticks, the points of which are driven into the ground to hold them in position. The distance between the stakes should be several times the height of the stake above the ground.



Another form requiring more labor but having much greater strength is called a "deadman," and consists of a log laid in a transverse trench with an inclined trench intersecting it at its middle point. The cable is passed down the inclined trench, takes several round turns on the log, and is fastened to it by half hitches and marlin stopping, Figs. 47, 48, 49. If the cable is to lead horizontally or inclined downward, it should pass over a log at the outlet of the inclined trench, Fig. 48. If the cable is to lead upward, this log is not necessary, but the anchor log must be buried deeper.



CHAPTER X

FIELD FORTIFICATIONS

1140. Object. The object of field fortifications is two-fold.

1. To increase the fighting power of troops by enabling the soldier to use his weapons with the greatest possible effect.

2. To protect the soldier against the enemy's fire.

1141. How these objects are accomplished.

These objects are accomplished:

1. By means of shelters—trenches, redoubts, splinterproofs, etc., which protect the soldier from the enemy's fire.

2. By means of obstacles—wire entanglements, abatis, pits, etc., which delay the advance of the enemy.

1142. Classification. Field fortifications are usually divided into three classes, hasty intrenchments, deliberate intrenchments and siege works.

Nomenclature of the Trench. The following illustration shows the names of the various parts of the trench.



1143. Hasty intrenchments include trenches dug by troops upon the battlefield to increase their fighting power. They are usually constructed in the presence of the enemy and in haste and embrace three forms viz:—the lying trench, the kneeling trench, and the standing trench.

1144. Lying trench. (Fig. 2.) This trench gives cover to a man lying down. When intrenching under fire the rifle trench can be constructed by a man lying down. He can mask himself from view in about 10 to 12 minutes and can complete the trench in 40 to 45 minutes. A good method is to dig a trench 18 inches wide back to his knees, roll into it and dig 12 inches wide alongside of it and down to the feet, then roll into the second cut and extend the first one back. Conditions may require men to work in pairs, one firing while the other uses his intrenching tool. Duties are exchanged from time to time until the trench is completed.



The height of the parapet should not exceed 1 foot. This trench affords limited protection against rifle fire and less against shrapnel.

1145. Kneeling trench. (Fig. 3.) Time permitting the lying trench may be enlarged and deepened until the kneeling trench has been constructed. The width of the bottom should be 2-1/2 feet—preferably 3 feet—and the relief (distance from bottom of trench to top of parapet) is 3 feet—the proper height for firing over in a kneeling position.



1146. Standing trench (Fig. 4) has a bottom width of 3 to 3-1/2 feet and a relief of 4-1/2 feet which is the proper firing height for men of average stature. As this trench does not give complete cover to men standing in it a passage way should be constructed in rear of it not less than 6 feet below the interior crest. This forms the complete trench (Fig. 5). Figures 6-7-8 show simple standing trenches used in the European War.



1147. Deliberate intrenchments comprise trenches and works constructed by troops not in line of battle and are usually intended to enable a small force to resist a much larger one. It frequently happens that hasty intrenchments are developed into deliberate intrenchments and from this stage pass into the domain of siege works.

1148. Fire trenches,—the trenches which shelter the firing line,—are of different types. No fixed type can be prescribed. The type must be selected with due regard to the terrain, enemy, time, tools, soil, etc., but all should conform to the requirements of a good field of fire, and protection for the troops behind a vertical wall, preferably with some head or over head cover.

The simplest form of fire trench is deep and narrow and has a flat concealed parapet (Fig. 9). When time will permit the simple trench should be planned with a view to developing it into a more complete form (Figs. 10 and 11). In all trenches as soon as practicable a passage way—2 feet wide at the bottom—should be provided, in rear of the firing step, for the men carrying supplies, ammunition, etc., and for the removal of the wounded.



When the excavated earth is easily removed a fire trench without parapet may be the one best suited to the soil and other conditions affecting the conditions of profile (Fig. 12). The enemy's infantry as well as artillery will generally have great difficulty in seeing this trench. Fig. 13 shows a squad trench. Fig. 14 shows a fire trench provided with protection against shrapnel. This trench is used in the European War.



In the European War the aim in constructing fire trenches seems to be to minimize and localize artillery effect as far as possible. The main excavation along the front is a continuous, very deep, communication, not in itself prepared for active defense. The actual firing is done from banquettes or firing steps just to the front of the passage or from trenches dug as far as 5 or 10 feet in front of the main excavation and reached by short passages. Figs 15 and 16 show the type of this construction. Fig. 17 shows a fire trench with parades and shelter.



1149. Traverses. Fire trenches are divided into sections or bays by means of traverses which intercept side or enfilade fire and limit the effect of shells, bombs or grenades, which burst inside of the trench. The traverses should be wide enough to screen the full width of the trench with a little to spare. The thickness of the traverse varies from 3 to 6 feet or more. Six feet is the dimension generally found in the traverses in the trenches on the European battle fronts.

1150. Trench recesses; sortie steps. It will be noted that in some of the diagrams of the trenches now being used in the European War the berm has been eliminated entirely. The object being to bring the firer closer to the vertical wall thus giving him better protection from shrapnel fire. There have also been added to the trench, recesses for hand grenades. These recesses are similar to recesses dug in the front wall of the trench for ammunition. One form of recess is shown in (Fig. 18). In order to provide facilities for rapidly mounting from the trench to charge, sortie steps and stakes have been provided in some trenches as shown in (Fig. 16).



1151. Parados. Instead of shrapnel, explosive shell is most frequently used in the European War. This necessitates the addition of a parados to the fire trench to protect against the back blast of high explosives. This is shown in (Figs. 8 and 17).

An interesting development in cover for the firing line is shown in dugouts constructed in the fire trenches in the European war. These dugouts are deep underground and shelter from 3 to 8 men each (Fig. 19). These dugouts will be discussed more in length under cover trenches.



1152. Head cover is the term applied to any horizontal cover which may be provided above the plane of fire. It is obtained by notching or loop-holing the top of the parapet so that the bottoms of the notches or loopholes are in the desired plane of fire. The extra height of parapet may be 12 to 18 inches and the loopholes may be 3 to 3-1/2 feet center to center.

Head cover is of limited utility. It increases the visibility of the parapet and restricts the field of fire. At close range the loopholes serve as aiming points to steady the enemy's fire and may do more harm than good at longer ranges. This is especially the case if the enemy can see any light through the loophole. He waits for the light to be obscured, when he fires, knowing there is a man's head behind the loophole. A background must be provided or a removable screen arranged so that there will be no difference in the appearance of the loophole whether a man is looking through it or not. Head cover is advantageous only when the conditions of the foreground are such that the enemy can not get close up.

1153. Notches and loopholes, Figs. 20-22, are alike in all respects, except that the latter have a roof or top and the former have not. The bottom, also called floor or sole, is a part of the original superior slope. The sides, sometimes called cheeks, are vertical or nearly so. The plan depends upon local conditions. There is always a narrow part, called the throat, which is just large enough to take the rifle and permit sighting. From the throat the sides diverge at an angle, called the splay, which depends upon the field of fire necessary.



The position of the throat may vary. If on the outside, it is less conspicuous but more easily obstructed by injury to the parapet and more difficult to use, since in changing aim laterally the man must move around a pivot in the plane of the throat. If the material of which the loophole is constructed presents hard surfaces, the throat should be outside, notwithstanding the disadvantages of that position, or else the sides must be stepped as in Fig. 22. In some cases it may be best to adopt a compromise position and put the throat in the middle, Fig. 22. Figs. 23 to 26 show details and dimensions of a loophole of sand bags.



A serviceable form of loophole consists of a pyramidal box of plank with a steel plate spiked across the small end and pierced for fire. Fig. 27 shows a section of such a construction. It is commonly known as the hopper loophole. The plate should be 3/8 in. thick, if of special steel; or 1/2 in., if ordinary metal. Fig. 28 shows the opening used by the Japanese in Manchuria and Fig. 29 that used by the Russians.



The construction of a notch requires only the introduction of some available rigid material to form the sides; by adding a cover the notch becomes a loophole. Where the fire involves a wide lateral and small vertical angle, loopholes may take the form of a long slit. Such a form will result from laying logs or fascines lengthwise on the parapet, supported at intervals by sods or other material, Fig. 31, or small poles covered with earth may be used, Fig. 30.



1154. Overhead cover. This usually consists of a raised platform of some kind covered with earth. It is frequently combined with horizontal cover in a single structure, which protects the top and exposed side. The supporting platform will almost always be of wood and may vary from brushwood or light poles to heavy timbers and plank. It is better, especially with brush or poles, to place a layer of sods, grass down, or straw, or grain sacks over the platform before putting on the earth, to prevent the latter from sifting through.



The thickness of overhead cover depends upon the class of fire against which protection is desired, and is sometimes limited by the vertical space available, since it must afford headroom beneath, and generally should not project above the nearest natural or artificial horizontal cover. For splinter proofs a layer of earth 6 to 8 ins. thick on a support of brush or poles strong enough to hold it up will suffice if the structure is horizontal. If the front is higher than the rear, less thickness is necessary; if the rear is higher than the front, more is required. For bombproofs a minimum thickness of 6 ins. of timber and 3 ft. of earth is necessary against field and siege guns, or 12 ins. timber and 6 ft. of earth against the howitzers and mortars of a heavy siege train, not exceeding 6 inches in caliber.

In determining the area of overhead cover to be provided, allow 6 sq. ft. per man for occupancy while on duty only, or 12 sq. ft. per man for continuous occupancy not of long duration. For long occupation 18 to 20 sq. ft. per man should be provided.

It is not practicable to give complete cover to rifle positions that will successfully withstand the heavy artillery of today. The use of overhead cover is usually limited to that sufficient for protection against rifle fire, machine gun fire, and shrapnel.

1155. Cover trenches are constructed to provide safe cover for the supports or reinforcements of the fire trenches or to provide cooking and resting facilities for the garrison of the neighboring fire trenches. The important point in cover trenches is safety. They vary in design from the simple rectangular trenches to elaborately constructed trenches having overhead cover, kitchens, shelters, latrines, dressing stations, etc. Cover trenches must not be mistaken for a secondary position, they are cover for the firing line, supports and reserves until they are required in the fire trenches. The cover trench requires a depth of at least 6 feet to protect men standing. Greater depths may be used when necessary. Fig. 36 is a section of an open cover trench and Fig. 37 of a closed one. This section may be used for a communicating trench. Fig. 38 shows a cover trench close to a fire trench. The character of overhead cover for trenches is shown in the diagrams under overhead cover. The distance of the cover trenches varies with the situation. The experience of the European war places the cover trenches from 15 to 50 yards in rear of the fire trenches. These trenches furnish shelter for at least 2/3 of the firing line and supports.



The reserves are furnished yet more elaborate shelter, with plenty of room for the men to lie down and rest and when practicable, bathing facilities are provided.

1156. Dugouts. An elaborate system of dugouts has developed along the lines occupied by the troops in the European war. These dugouts are located from 14 to 40 feet below the ground and are reached by stairs in timbered passage ways. At the foot of the stairs a tunnel or corridor runs forward and on either side or at the end, rooms have been dug out varying in size. Most of these rooms have been timbered and lined. Many are electrically lighted. In some of these underground shelters, accommodations for several hundred men have been prepared with all of the necessary facilities for making them comfortable. It must be understood that such elaborate preparations can only be made when troops face each other in trenches where operations have developed into practically a siege.

1157. Communicating trenches. These trenches as the name implies are for the purpose of providing safe communication between the cover and fire trenches. They may be also constructed just in rear of a series of fire trenches to provide a means of communication from one to the other. Communicating trenches also extend to the rear of the cover trenches and provide safe passage to fresh troops or supplies. These trenches are usually laid out in zig zag or curved lines (Fig. 39), to prevent enfilade fire from sweeping them. As a general rule excavated earth is placed on both sides of the trench to afford protection, the depth is usually from 6 to 7 feet. (Fig. 15) shows a typical communicating trench.



1158. Lookouts. To enable the garrison of a trench to get the greatest amount of comfort and rest, a lookout should be constructed and a sentinel stationed therein.

The simplest form would consist of two sandbags placed on the parapet and splayed so as to give the required view, and carefully concealed.

Better forms may be constructed, with one side resting on the berm by using short uprights with overhead cover, a slit on all sides being provided for observation.

At night, lookouts are usually posted at listening points located in or beyond the line of obstacles. These will be discussed under obstacles.

1159. Supporting Points. In some cases small supporting points may have to be established close behind the general line of trenches for the purpose of breaking up a successful attack on the trenches and to aid in delivering a counter attack. These points are strongly entrenched and have all around wire entanglements and are garrisoned by from 20 to 40 picked men or by larger forces if the situation demand it. In some cases machine guns are added to the force in the supporting point.

1160. Example of trench system. Having discussed trenches and obstacles somewhat in detail, let us take a combination of the whole showing a complete system such as is used today. (Fig. 40) is a good example.



Beginning at the front we have the line of wire entanglements or obstacles with their listening posts X, for guarding them. Connecting the listening posts to the fire trenches are the communicating trenches. The fire trenches are shown by the heavy black line running about 60 feet in rear of the obstacles. Note the many traverses shown by the indentations in the line. Points marked M with arrows projecting to the flanks are machine guns, so located as to sweep the front of the position with a cross fire. Points marked S are underground shelters for from 3 to 6 men. Points marked S' are shelters for 30 men. In rear of the firing trenches at a distance varying from 100 to 200 feet is the line of cover trenches. This line is connected with the fire trenches by the zig zagged line of communicating trenches. Note that the latrines (L) and first aid stations (F) are just off from the communicating trenches, while the larger shelter for men (S') are near the cover trenches. As the note on the diagram shows, the trench requires 250 men to occupy it with double that number in support. The trench has 108 loopholes with spaces between provided with a higher banquette so that the whole parapet may be manned for firing.

On the battlefields of Europe today there are generally three lines of fire trenches. This permits the defender to fall back to a 2nd or 3rd prepared position in case he is driven out of his first trench. On a hill we find a fire trench near the foot of the slope, one just forward of the military crest, and the third on the reverse slope of the hill.

In many instances the first line trenches consist of as many as four or five lines of trenches running in a general lateral direction and connected by deep narrow communicating trenches. The depth between the first and last of these trenches is, in some instances, not over a hundred yards. Sign boards are necessary at short intervals to prevent the soldiers from getting lost. The effect of having so many alternative firing trenches is to make it extremely difficult for an enemy to advance from, or even to hold one of them, even when he gains a footing, as he would be swept by fire from the supporting trenches in rear and also by flanking fire from the adjacent trenches.

1161. Location. There are two things to be considered in locating trenches: (1) The tactical situation, and (2) the nature of the ground. The first consideration requires that the trenches be so located as to give the best field of fire. Locating near the base of hills possesses the advantage of horizontal fire, but, as a rule, it is difficult to support trenches so located and to retreat therefrom in case of necessity. While location near the crest of hills—on the "military crest"—does not possess the advantage of horizontal fire, it is easier to support trenches so located and to retreat therefrom. Depending upon circumstances, there are times when it will be better to intrench near the base of hills and there are other times when it will be better to intrench on the "military crest," which is always in front of the natural crest. The construction of trenches along the "military crest" does not give any "dead space"—that is, any space to the front that can not be reached by the fire of the men in the trenches.

Whether we should construct our trenches on high or low ground is a matter that should always be carefully considered under the particular conditions that happen to exist at that particular time, and the matter may be summarized as follows:

The advantages of the high ground are:—

1. We can generally see better what is going on to our front and flanks; and the men have a feeling of security that they do not enjoy on low ground.

2. We can usually reenforce the firing line better and the dead and wounded can be removed more easily.

3. The line of retreat is better.

The disadvantages are:—

1. The plunging fire of a high position is not as effective as a sweeping fire of a low one.

2. It is not as easy to conceal our position.

The advantages of low ground, are:—

1. The low, sweeping fire that we get, especially when the ground in front is fairly flat and the view over the greater part of it is uninterrupted, is the most effective kind of fire.

2. As a rule it is easier to conceal trenches on low ground, especially from artillery fire.

3. If our trenches are on low ground, our artillery will be able to find good positions on the hill behind us without interfering with the infantry defense.

The disadvantages are:—

1. As a rule it will be more difficult to reenforce the firing line and to remove the dead and wounded from the trenches.

2. On a low position there will usually be an increase of dead space in our front.

3. The average soldier acting on the defensive dreads that the enemy may turn his flank, and this feeling is much more pronounced on low ground than on high ground. Should the enemy succeed in getting a footing on our flank with our trenches on top of the hill, it would be bad enough, but it would certainly be far worse if he got a footing on top of the hill, on the flank and rear, with our company on low ground in front. We, therefore, see there are things to be said for and against both high and low ground, and the most that can be said without examining a particular piece of ground is: Our natural inclination is to select high ground, but, as a rule, this choice will reduce our fire effect, and if there is a covered approach to our fire trenches and very little dead ground in front of it, with an extensive field of fire, there is no doubt the lower ground is better. However, if these conditions do not exist to a considerable degree, the moral advantage of the higher ground must be given great weight, especially in a close country.

The experience of the European war emphasizes the fact that the location of rifle trenches is today, just as much as ever, a matter of compromise to be determined by sound judgment on the part of the responsible officers. The siting of trenches so that they are not under artillery observation is a matter of great importance, but, it has yet to be proven that this requirement is more important than an extensive field of fire. There are many instances where to escape observation and fire from the artillery, trenches were located on the reverse slopes, giving only a limited field of fire. This restricted field of fire permitted the enemy to approach within a few hundred yards of the trench and robbed them of the concealment they had hoped to gain. The choice between a site in front, and one in rear of a crest, is influenced by local conditions which govern the effectiveness of our own and the enemy's fire. In general, the best location for effective fire trenches, lies between the military crest of rising ground and the lowest line from which the foreground is visible. If the position on the military crest is conspicuous, it is inadvisable.

With regard to the nature of the ground, trenches should, if practicable, be so located as to avoid stony ground, because of the difficult work entailed and of the danger of flying fragments, should the parapet be struck by an artillery projectile.

To locate the trace of the trenches, lie on the ground at intervals and select the best field of fire consistent with the requirements of the situation.

Trenches should be laid out in company lengths, if possible, and adjoining trenches should afford each other mutual support. The flanks and important gaps in the line should be protected by fire trenches echeloned in rear.

1162. Concealment of trenches. Owing to the facilities for observation that the aeroplanes and other air craft afford, and to the accuracy and effect of modern artillery fire, every possible means should be taken to conceal trenches, gun implacements, and other works. The aim should be to alter the natural surface of the ground as little as possible and to present a target of the smallest possible dimensions. Covering the parapet with brush or grass will afford temporary concealment. If the new earth can be sodded it aids greatly in concealing the trench. In some cases troops have gone to the extent of painting canvas to resemble the ground and have placed it over trenches, guns, etc. Straw and grass placed in the bottom of trenches make them less conspicuous to air scouts. When trenches are dug on a fairly steep slope care must be used to conceal the back of the trench, which, being higher than the parapet, will stand out as a scar on the hillside. Grass or brush may be used to conceal the back of the trench.

1163. Dummy trenches. May be constructed which attract the enemy's attention and draw his fire, or at least a part of it. The extent to which this method may be used may include the construction of dummy obstacles and guns, and even hats may be placed on the parapets.

1164. Length of trench. The usual minimum allowance of trench space is one yard per man, although in some tests, two feet was found sufficient for men to fire satisfactorily. Ordinarily one squad will occupy the space between two traverses which experience has shown should be about 15 feet apart.

1165. Preparation of the foreground. One of the first principles in improving the foreground is that an enemy attacking the trenches shall be continually exposed to fire especially in the last 400 or 500 yards. This requires a clearing of the foreground and a filling in of depressions or leveling of cover. Dead space may be swept by fire of trenches specially located for that purpose. Those features of the ground which obstruct the field of fire, restrict the view, or favor or the enemy's approach, should be removed as far as possible. On the other hand, features which favor the concealment of the trenches or increase the difficulty of the attack would better be left standing, especially when it is possible to fire through or over them.

1166. Revetments. By a revetment we mean a facing placed against the front or back wall of a trench to keep the earth in place.

When trenches are to be occupied for any length of time, they must be revetted. There are many forms of revetments. Sod revetments, stakes with brush behind them, stakes with planks, boards, or poles behind them and a common form seen in the trenches in Europe chicken wire with brush or canvas behind it.

1167. Drainage. All trenches should be dug so as to drain in case of rain. In favorable locations the trench may be constructed to drain automatically, by constructing it with an incline to one end. Under ordinary circumstances dry standing has to be provided in trenches by raising the foot level by the use of brush, boards, poles, etc. Bailing will have to be resorted to in most cases to drain the trench.

1168. Water Supply. At least 1/2 a gallon of water per man per day should be supplied. The supply is almost invariably liable to be contaminated, therefore, it should be sterilized by boiling or by treating. These are usually located just off from the communicating trenches. Some form of receptacle should be used and all deposits covered with chemicals.

1169. Latrines. Numerous latrines must be constructed in the trenches' earth. These receptacles are removed from time to time and emptied in pits dug for that purpose. Urinal cans must also be provided and cared for in a similar manner.

1170. Illumination of the Foreground. Battlefield illumination is a necessity where night attacks may be expected, and also as a protection to the line of obstacles. Portable searchlights have become an accepted part of every army. In addition to these, trenches must be supplied with reflector lights, star bombs, rockets and flares, arranged so that they can be put into action instantaneously when the enemy approaches.

The foreground should be entirely illuminated, leaving the defenders in the shadow. If the light is too close to the defenders parapet, they are illuminated and become a good target. Some flares will burn for 20 minutes and may be thrown to the front as grenades, fired as rockets, shot from small mortars, or placed well to the front to be set off by trip wires close to the ground. The best light devised is one that can be fired well to the front from a small mortar and then hung suspended from an open parachute above the enemy. Bonfires can be laid ready for lighting when no other means is at hand. Whatever form of illumination is adopted, it should withstand bad weather conditions and prolonged bombardment.

1171. Telephones. When armies have been forced to trench warfare and time has permitted an elaborate system of trenches to be constructed, telephone communication is established as soon as possible. The central station, with the switch-board is located in a shelter in rear of the cover trenches and lines are run to all trenches, lookout stations and listening points.

1172. Siege works. Comprise devices used by besiegers and besieged in attack and defense of strong fortifications and especially those devices enable troops to advance under continuous cover.



CHAPTER XI

OBSTACLES

1173. Object. The main objects in placing obstacles in front of the trenches are, to protect them from surprise, and to stop the enemy's advance or to delay him while under the defender's fire.

1174. Necessity for obstacles. It is evident that the present tendency is to reduce the number of men assigned to constant occupancy of the first line trenches. This is due to the effectiveness of rifle fire at close range, the destructive effect of shell and shrapnel, the infrequency of daylight attack on intrenched positions, and the severe strain on the men. The aim seems to be the placing here and there of a lookout or trench guards, who, when necessity demands can call help from the near by splinterproofs, dugouts, etc., before the enemy can make his way through the obstacles. It has been found from experience in the European war that as long as shells are directed at the trenches no danger of attack is feared but, when the shells are concentrated against the obstacles the trenches are manned and preparations are made to resist an assault.

1175. Location. Obstacles must be so located that they will be exposed to the defenders' fire, and should be sheltered as far as possible from the enemy's artillery fire. They should be difficult to remove or destroy, should afford no cover for the enemy, and should not obstruct counter attacks. No obstacle should be more than 100 yards from the defender's trench. Care must be taken not to place them so close to the trench that hand grenades can be thrown into the trench from beyond the obstacle. Obstacles may be placed in one, two or three lines. As far as possible they should be concealed so that they will not betray the location of the trench.

1176. Kinds of Obstacles. The following are the most common kinds of obstacles:—

Abatis consisting of trees lying parallel to each other with the branches pointing in the general direction of approach and interlaced. All leaves and small twigs should be removed and the stiff ends of branches pointed.

Abatis on open ground is most conveniently made of branches about 15 feet long. The branches are staked or tied down and the butts anchored by covering them with earth. Barbed wire may be interlaced among the branches. Successive rows are placed, the branches of one extending over the trunks of the one in front, so as to make the abatis 5 feet high and as wide as desired. It is better to place the abatis in a natural depression or a ditch, for concealment and protection from fire. If exposed to artillery, an abatis must be protected either as above or else by raising a glacis in front of it. Fig. 1 shows a typical form of abatis with a glacis in front. An abatis formed by felling trees toward the enemy, leaving the butt hanging to the stump, the branches prepared as before, is called a slashing, Fig. 2. It gives cover, and should be well flanked.



1177. A palisade is a man-tight fence of posts. Round poles 4 to 6 inches in diameter at the large end are best. If the sticks run 5 to 8 inches, they may be split. If defended from the rear, palisades give some shelter from fire and the openings should be made as large as possible without letting men through. If defended from the flank, they may be closer, say 3 to 4 inches apart. The top should be pointed. A strand or two of barbed wire run along the top and stapled to each post is a valuable addition.

Palisading is best made up in panels of 6 or 8 feet length, connected by a waling piece, preferably of plank, otherwise of split stuff. If the tops are free, two wales should be used, both underground. If the tops are connected by wires, one will do.

Palisades should be planted to incline slightly to the front. As little earth should be disturbed in digging as possible, and one side of the trench should be kept in the desired plane of the palisade. If stones can be had to fit between the posts and the top of the trench, they will increase the stiffness of the structure and save time in ramming, or a small log may be laid in the trench along the outside of the posts. Figs. 3 and 4 show the construction and placing of palisades.



1178. A fraise is a palisade horizontal, or nearly so, projecting from the scarp or counterscarp. A modern and better form consists of supports at 3 or 4 feet interval, connected by barbed wire, forming a horizontal wire fence. Fig. 5.



1179. Cheveaux de frise are obstacles of the form shown in Fig. 6. They are usually made in sections of manageable length chained together at the ends. They are most useful in closing roads or other narrow passages, as they can be quickly opened for friendly troops. The lances may be of iron instead of wood and rectangular instead of round; the axial beam may be solid or composite. Figs. 8 and 9 show methods of constructing cheveaux de frise with dimension stuff.



1180. A formidable obstacle against cavalry consists of railroad ties planted at intervals of 10 feet with the tops 4-1/2 feet above the ground, and connected by a line of rails spiked securely to each, Fig. 7. The rail ends should be connected by fish plates and bolted, with the ends of the bolts riveted down on the ends.

Figs. 10 and 11 show forms of heavy obstacles employed in Manchuria by the Russians and Japanese, respectively. The former is composed of timber trestles, made in rear and carried out at night. The latter appears to have been planted in place.



1181. A wire entanglement is composed of stakes driven in the ground and connected by wire, barbed is the best, passing horizontally or diagonally, or both. The stakes are roughly in rectangular or quincunx order, but slight irregularities, both of position and height should be introduced.

In the high entanglement the stakes average 4 feet from the ground, and the wiring is horizontal and diagonal, Fig. 12.



The low wire entanglement has stakes averaging 18 inches above the ground and the wire is horizontal only. This form is especially effective if concealed in high grass. In both kinds the wires should be wound around the stakes and stapled and passed loosely from one stake to the next. When two or more wires cross they should be tied together. Barbed wire is more difficult to string but better when done. The most practicable form results from the use of barbed wire for the horizontal strands and smooth wire for the rest.

This is the most generally, useful of all obstacles because of the rapidity of construction, the difficulty of removal, the comparatively slight injury from artillery fire, and its independence of local material supplies.

1182. Time and materials. One man can make 10 sq. yds. of low and 3 sq. yds. of high entanglement per hour. The low form requires 10 feet of wire per sq. yd. and the high 30 feet. No. 14 is a suitable size. The smooth wire runs 58.9 ft. to the lb. A 100-lb. coil will make 600 sq. yds. of low or 200 sq. yds. of high entanglement. If barbed wire is used, the weight will be about 2-1/2 times as much.

1183. Wire fence. An ordinary barbed-wire fence is a considerable obstacle if well swept by fire. It becomes more formidable if a ditch is dug on one or both sides to obstruct the passage of wheels after the fence has been cut. The fence is much more difficult to get through if provided with an apron on one or both sides, inclined at an angle of about 45 deg., as indicated in Figs. 13 and 14. This form was much used in South Africa for connecting lines between blockhouses. When used in this way the lines of fence may be 300 to 600 yds. long, in plan like a worm fence, with the blockhouse at the reentrant angles. Fixed rests for rifles, giving them the proper aim to enfilade the fence, were prepared at the blockhouses for use at night.



Such a fence may be arranged in many ways to give an automatic alarm either mechanically or electrically. The mechanical forms mostly depend on one or more single wires which are smooth, and are tightly stretched through staples on the posts which hold them loosely, permitting them to slip when cut and drop a counterweight at the blockhouse, which in falling explodes a cap or pulls the trigger of a rifle.

1184. Military pits or trous de loup are excavations in the shape of an inverted cone or pyramid, with a pointed stake in the bottom. They should not be so deep as to afford cover to the skirmisher. Two and one-half feet or less is a suitable depth. Fig. 15 shows a plan and section of such pits.



They are usually dug in 3 or 5 rows and the earth thrown to the front to form a glacis. The rear row is dug first and then the next in front, and so on, so that no earth is cast over the finished pits.

An excellent arrangement is to dig the pits in a checkerboard plan, leaving alternate squares and placing a stake in each of them to form a wire entanglement, Fig. 16. One man can make 5 pits on a 2-hour relief.



1185. Miscellaneous barricades. Anything rigid in form and movable may be used to give cover from view and fire and to obstruct the advance of an assailant. Boxes, bales and sacks of goods, furniture, books, etc., have been so used. The principles above stated for other obstacles should be followed, so far as the character of the materials will permit. The rest ingenuity must supply. Such devices are usually called barricades and are useful in blocking the streets of towns and cities.

1186. Inundations. Backing up the water of a stream so that it overflows a considerable area forms a good obstacle even though of fordable depth. If shallow, the difficulty of fording may be increased by irregular holes or ditches dug before the water comes up or by driving stakes or making entanglements. Fords have frequently been obstructed by ordinary harrows laid on the bottom with the teeth up.

The unusual natural conditions necessary to a successful inundation and the extent and character of the work required to construct the dams make this defense of exceptional use. It may be attempted with advantage when the drainage of a considerable flat area passes through a restricted opening, as a natural gorge, a culvert, or a bridge.

Open cribs filled with stones, or tighter ones with gravel or earth may form the basis of the obstruction to the flow of water. The usual method of tightening cracks or spaces between cribs is by throwing in earth or alternate layers of straw, hay, grass, earth, or sacks of clay. Unless the flow is enough to allow considerable leakage, the operation will not be practicable with field resources.

When the local conditions permit water to be run into the ditch of a parapet it should always be done.

1187. Obstacles in front of outguards should be low so they cannot be seen at night. A very simple and effective obstacle can be made by fastening a single strand of wire to the top of stout stakes about a foot high, and then placing another wire a little higher and parallel to, and about one yard in rear of, the first. The wires must be drawn tight, and securely fastened, and the stakes fairly close together, so that if the wire is cut between any two stakes the remainder will not be cut loose. Any one approaching the enemy will trip over the first wire, and before he can recover himself he will be brought down by the second. In the absence of wire, small sapplings may be used instead. Of course, they are not as good as wire, but it does not take much to trip up a man in the dark.



Lessons from the European War

What follows is based on reports from the battle fronts in Europe.

1188. Wire entanglements. The war in Europe has proven that the wire entanglements are the most important and effective obstacle yet devised. Owing to the intensity of the opposing fire and in many cases to the short distance between the opposing trenches, it has become necessary to construct all forms of obstacles in portable sections which are carried or rolled quickly into place, either by soldiers rushing out in day light and quickly staking the obstacles down or by placing the obstacles quietly at night.

For placing wire entanglements at night, an iron post has been devised about 1/4 of an inch in diameter, with eyelets for attaching the wire. The lower 18 inches is made as an auger, so that the posts can be quietly screwed into the ground at night and the wire attached. Another method of placing wire entanglements is to make them in sections and roll them up. These sections are usually about 20 feet long, the wire firmly fastened to the sharpened stakes. At a favorable moment the soldiers rush out, unrolling the sections as they go and with mauls quickly drive the stakes. Loose ends of wire enable the sections to be bound together as placed.

Another form of wire entanglement is shown in (Fig. 18). Triangular pyramids 3 feet 6 inches high are made of poles or timber. The pyramids are usually arranged in pairs with the wire on three faces so that, no matter if the obstacle is rolled over, a wire fence is presented. These obstacles are carried out and placed so as to break joints and are staked down as soon as possible.



The wire used for entanglements is found more convenient to handle when wound on a stake a yard in length, in a sort of figure eight winding. Special barbed wire of heavier material and barbs placed close together has been found much more effective than the commercial barbed wire.

In some localities electrified wire has been used. In such cases the obstacle is charged in sections, so that, if one section is grounded it will not affect the others.

1189. Wire cheveaux de frise. Two forms of this obstacle have appeared. Both are portable. They consist of two or more wooden crosses fastened at their centers to a long pole and connected with each other by barbed wire. This obstacle retains its effectiveness when rolled over. (Figs. 19 and 20) give an idea of their construction. The form shown in (Fig. 19) is often made small enough for individuals to carry. These are prepared in the trenches and used for throwing into one's own entanglements to make them more complex or may be carried when making an assault and thrown into the enemy's trenches to prevent movements from one part of the trench to another. The long stick projects out of the end to be used as a handle.



1190. Guarding obstacles. It has been found necessary to keep a constant watch over obstacles after they have been placed.

1191. Listening posts. One of the best methods is to post one or more men in listening posts in or beyond the line of obstacles. These listening posts are rifle pits with over head cover, fully protected from fire from the rear as well as front, and loop holes for observation and fire. They are connected with the fire trenches by means of a covered communication or even tunnels in some cases and are provided with some form of prompt communication with the firing trenches by telephone, bell or other means. The communicating trench or tunnel is provided with a strong door which may be closed to prevent an enemy from securing access to the fire trench, in case the lookout is surprised. Pits with trap doors are also used to prevent an enemy from creeping up the tunnel to the fire trench.

These lookouts can give early warning of the approach of an enemy, either for the purpose of assault or cutting through the obstacles. In many instances they have detected mining operations of the enemy by hearing the blows of picks under ground.

1192. Automatic alarms. Many automatic alarms have been used to give warning of attack on the obstacles. These vary from the simple setting of a pistol or rifle, which is fired when the enemy attempts to cut through the entanglement, to intricate electrical alarms.

1193. Searchlights. Searchlights have been provided so that, the instant an alarm is given the obstacles are flooded by a brilliant light and the enemy exposed to fire.



CHAPTER XII

TRENCH AND MINE WARFARE[14]

1194. Asphyxiating gases. The asphyxiating gases employed may be divided into three general classes, viz:

Suffocating gases, the most common of which are carbonic and nitrogen.

Poisonous gases, under which head come carbon monoxide and cyanogen.

Gases which affect the throat and bronchial tubes, such as chlorine and bromine. The latter class is most commonly employed.

The methods usually employed for liberating these gases are to have a plant some distance in rear of the trenches where the gas is stored under pressure and carried to the trenches through pipes, where it can be liberated towards the enemy's trenches when there is a favorable wind to carry it along; or, the gas may be carried in cylinders or other containers and liberated at the desired points. Hand grenades or bombs are also employed which, upon bursting, liberate the gas or in some cases scatter acids or caustic soda. Some of these bombs contain a chemical which when liberated affects the eyes, causing impaired vision. The Germans employ several kinds of shell containing gases of different densities, one of heavy gas fired as a curtain to the rear to permit reinforcement of the trenches and another of lighter gas to demolish the trenches and destroy the firing line. As a general rule these gases are employed when the fire trenches of the opposing forces are close together though the shell containers may be used at long ranges. All of these gases being heavier than air lie close to the ground and flow over and down into the trenches.

1195. Protection against gases. The best protection against these gases, is a mask of some kind. The commonest form employed is a flexible mask that conforms to the head, is fitted with glass for seeing through, and has an arrangement of tubes and valves which require the wearer to inhale through his nose and exhale through his mouth.

These masks have an absorbent composed of hyposulphite of sodium or of 72 per cent of the nitrous thiosulphate and 28 per cent of bicarbonate of soda. This absorbent placed so that air must be breathed through it, neutralizes the acids in the gases. Soldiers are provided with these masks, sometimes with two of them, and are required to have them renewed every three months.

Trench sprays may be used to spray neutralizing liquid in the trenches to kill the gases.

The favorable conditions for the employment of gases are wind blowing toward the enemy's trenches and warm weather. Unfavorable conditions are rain, cold, and adverse winds.

In some localities weather vanes placed in the direction of the enemy's trenches and arranged so that they may be watched at night give an indication of favorable winds and enable the defender to prepare for a gas attack.

Before the masks were provided bonfires were prepared of oil soaked materials which; when ignited, produced an intense heat and the resulting column of air diverted the gas clouds.

1196. Liquid fire. By use of hand or motor driven pumps, and a light grade of petroleum, columns of liquid fire may be squirted into the opposing trenches. If the oil should fail to remain lighted it may be fired by bursting hand grenades or throwing fire balls into the trenches. This means of attack is employed when opposing trenches are close together.

As a defense measure ditches may be dug in front of the trenches and filled with a porous material which is then soaked with oil. Heavy oils, being hard to ignite, are not dangerous to the defense, and will remain with little loss for a long time. To make sure of prompt ignition gas lines are laid in the ditches. When turned on the gas readily ignites and the resulting fire produces great heat. Wire or barbed wire looped in the ditches and staked down makes this a formidable obstacle.

1197. Grenades and bombs are containers, designed to be thrown by hand, by a sling, fired as a rocket or from specially constructed mortars, or dropped from aerial craft. They burst by time or percussion fuses and may be improvised in a variety of forms and are most useful in close attack or defense. Their effect is local but they are very demoralizing to men's nerves.

1198. Hand grenades are designed to be thrown by the hand and vary greatly in construction. In general, however, they consist of a container filled with bullets or pieces of iron or other metal in the center of which is a charge of high explosive which scatters the bullets or fragments with deadly effect. The three methods of discharging a hand grenade are:

By time fuse which is lighted by hand. About 5 to 9 seconds is the time from ignition until the grenade bursts. This does not give the defender time to pick up the bomb and throw it out of the trench.

By friction primer and fuse. In this form of hand grenade a strap on the wrist with a short line attached with a hook on the end of it serves, when the hook is engaged in the ring of the grenade, to jerk the primer when the grenade is thrown. This automatically ignites the fuse which bursts the grenade in from 4 to 5 seconds.

By percussion. In this form of grenade the charge is fired when the grenade strikes the ground or object at which it is thrown. In this form of grenade a safety pin holds the plunger from the cap. When the grenade is to be thrown the safety pin is withdrawn.

As a general rule fuse burns at the rate of 1 inch in 1 and 1/4 seconds; however each lot of fuse should be tested.

Figs. 1 and 2 show two forms of improvised grenades. Common cans, such as preserved fruits and vegetables are shipped in commercially, make good containers. The usual weight of a hand grenade is about 1-1/2 pounds.



1199. Other methods of throwing grenades. Many grenades have been designed to be fired from the ordinary rifle. This grenade has a rod which is inserted in the barrel of the rifle. A special charge of powder is used in the cartridge from which the bullet has been withdrawn.

Common slings, catapults, and other devises have been frequently used.

1200. Aerial mines. (Fig. 3.) This form of grenade is very heavy, often weighing 200 pounds and is fired from a trench mortar.



1201. Winged torpedo. (Fig. 4.) This projectile is fitted with three winged vanes which steady its flight and greatly increase the accuracy. A rod fitted into its base enables it to be fired from a comparatively small trench, mortar. The torpedo weighs about 40 pounds and the mortar 200 pounds. The mortar, being light, can be carried from one part of the trench to another by two men.



The aerial mine and winged torpedo may be used effectively to beat down the enemy's defenses, destroying his sand bags and trenches, and cutting away wire entanglements and other obstacles. The winged torpedo having a greater range (500 yards) and being more accurate, is the more effective.

1202. Bombs from air-craft are some form of high explosive bomb which burst on striking. Another type of bomb used by aeroplanes consists of a container filled with steel darts. The bursting charge is fired by a fuse. The operator usually cuts the fuse so that the bomb will burst at a considerable altitude. The steel darts are scattered in all directions and have sufficient velocity to pass through a man or horse.

1203. Protection against hand grenades. (Fig. 5.) For protection against hand grenades and bombs a screen of wire netting may be erected in front of the trenches and arranged at such a slope that most of the grenades passing over the screen will clear the trench while those striking the netting will roll away from the trench. This protection is very satisfactory for communications, machine gun emplacements, etc., but, is of doubtful value in fire trenches as it does not permit an easy offensive by the defenders.



1204. Tanks. The so-called "tanks," first used by the British armies in the battle of the Somme in September, 1916, are in reality armored caterpillar tractors carrying machine guns and capable of traversing rough ground, smashing down trees and entanglements, and passing across the ground between the opposing trenches over the shell holes made by the opposing artillery.

The machinery, guns and crew are contained in an armored body and the two tractor belts extend to full length on either side, being so arranged that the tank can climb a steep slope. From the meager data obtainable it would appear that the tanks carry from 4 to 6 machine guns in armored projections built out from the sides. These are provided with revolving shields permitting two guns to fire in any direction at one time.

The principle of the tractor is similar to that of those manufactured in the United States and used commercially in reclamation work. The addition of the armored body and guns makes the "military tank."

These "tanks" have proven of great value in village fighting, by smashing down barricades and driving machine guns from their positions in cellars and houses. They have also been used with some success in destroying obstacles.

The power of these new engines may be judged from their ability to smash down trees six inches in diameter and by means of cables to uproot trees as large as 15 inches in diameter.

These "tanks" are proof against rifle and machine gun fire, but are unable to withstand even light artillery.

1205. Helmets. Steel helmets made their appearance in the European war in 1915, as a protection to the soldier's head against rifle, machine gun and shrapnel fire. So successful were they that they are being furnished to all troops on the battlefield. Already several millions have been supplied. Where heretofore head wounds accounted for over 20 per cent of the casualties in trench warfare, the percentage has been reduced by the wearing of helmets to about one half per cent. While the helmet does not afford complete protection against rifle and shrapnel fire, it has been found that hits result only in severe concussion, where before fatal wound resulted. These helmets are painted khaki color.

1206. Masks. Steel masks for sentinels and snipers have been adopted by the Germans. This mask covers the head and face with curved surfaces which deflect bullets. Small eye holes permit a clear view of the target and a small section is omitted in the lower right side to permit bringing the rifle against the cheek in firing.

1207. Periscopes. Periscopes have been universally adopted in trench warfare for observing the enemy while keeping completely under cover. It is a simple arrangement of two mirrors in a vertical tube. The upper reflects the image of the object to the lower mirror which in turn reflects it to the eye of the observer. By raising the top of the periscope above the parapet the soldier can watch the foreground while at the same time remaining completely concealed himself.

A more elaborate periscope for the control of artillery fire has a collapsible tube which may be extended and elevated to a height of 75 feet.

1208. Sniperscope. This is a combination of the periscope and rifle by means of which a soldier can aim and fire his piece at an object without exposing himself above the parapet.

1209. Aids to firing. Rifles laid in notched boards placed in the parapet may be sighted and prepared for night firing, or a wire stretched just outside of the loophole on which the barrel of the rifle can rest when in the proper firing position to cover certain points, enables the soldier to fire effectively at night when it is too dark to aim.

1210. Mining. Military mining consists of digging communications and chambers underground and placing therein charges of explosives and firing such charges. Mining is slow and restricted in its application and therefore this method of attack is used against very strong points of the enemy's line,—a salient, a building, or other point,—held in great force. The aim in mine warfare is to make a sudden breach in the enemy's trench, destroy the flanking supports which could be used to stop this breach and then to take the trench by assault and organize it for defense before the enemy's forces, disorganized from the explosion, can recover.

Sometimes mines are placed in front of the trenches and exploded electrically when the enemy reaches them in attempting an assault.

1211. Countermining. The enemy, when mining operations are suspected, runs out tunnels to meet the opposing mine. Sometimes listening galleries are driven underground and men posted to detect the sound of mining operations. Once the direction of the opposing tunnel is discovered a charge of explosive is laid across its approach and fired at a moment when it will cause the most damage.

FOOTNOTES:

[14] To those desiring to go into the subject of trench warfare in detail, the author would recommend "Trench Warfare," by himself. George Banta Publishing Co., Menasha, Wis.; $1.25.



CHAPTER XIII

MARCHES

(Based on Infantry Drill Regulations and Field Service Regulations)

1212. Marching principal occupation of troops in campaign. Marching constitutes the principal occupation of troops in campaign and is one of the causes of heaviest loss. This loss, however, may be materially reduced by proper training and by carrying out strictly the rules regulating the conduct of marches, especially the rules of march discipline.

1213. Physical training; hardening new troops. By systematic and progressive physical exercises and actual marching, Infantry can be accustomed to the fatigue of bearing arms and equipment.

With new or untrained troops, the process of hardening the men to this work must be gradual. It should begin with ten-minute periods of vigorous setting-up exercises three times a day to loosen and develop the muscles. One march should be made each day with full equipment, beginning with a distance of 2 or 3 miles and increasing the distance daily as the troops become hardened, until a full day's march under full equipment may be made without exhaustion.

1214. Long march not to be made with untrained troops. A long march should not be made with untrained troops. If a long distance must be covered in a few days, the first march should be short, the length being increased each succeeding day.

1215. A successful march. A successful march, whether in peace or war, is one that places the troops at their destination at the proper time and in the best possible physical condition. Therefore, every possible effort, by exercising care and judgment, and by enforcing march discipline, must be made by all officers and noncommissioned officers to have the troops reach their destination in good physical condition,—"ready for business."

Preparation

1216. The commander. The commander must give such instructions as will insure that the necessary preparations are made,—that the men and animals are in fit condition and that the men are properly equipped; that provision has been made for rations and ammunition; that the wagons are properly loaded; that the necessary arrangements have been made for caring for the sick, etc.

1217. Organization commanders. Every organization commander is responsible that such of the above requirements as apply to his organization are complied with.

1218. Filling canteens. It is an invariable rule that all canteens must be filled before the march begins.

Starting

1219. Time to start. When practicable, marches begin in the morning, ample time being allowed for the men to breakfast, animals to feed, and the wagons or animals to be packed.

The time for reveille, if different from the usual hour, should be announced the evening before.

The exact hour for the start depends, of course, upon circumstances. However, as a rule, foot troops do not start before broad daylight; mounted troops, when practicable, about an hour after broad daylight.

In order to avoid intense heat, especially in the tropics, and also, in the case of long marches, to avoid reaching destination after dark, an earlier start than usual must be made.

Both men and animals rest well in the early morning hours, and should not, therefore, have this rest interrupted unless there is some real necessity for it.

Starting at night or at an hour that will cause a part of the march to be made at night, should, if possible, be avoided, because of the difficulties and disadvantages of night marching.

Conduct of the march

1220. The rate of march. The rate of march varies with the length of march, kind of troops, equipment carried, size of command, condition of troops, state of the weather, condition of roads, and other circumstances. However, whatever the rate may be it should be uniform, that is most important, as there is nothing that will irritate and tire a command more than a varying, un-uniform rate of march.

The rate of march is regulated by the commander of the leading company or some one designated by him, who should give the matter special attention, the rate being checked from time to time by a watch.

On a march of several days' duration the position of companies is ordinarily changed daily, so that each in turn leads.

With trained troops, in commands of a regiment or less, marching over average roads, the rate should be from 2-3/4 to 3 miles per hour. With larger commands carrying full equipment, the rate will be from 2 to 2-1/2 miles per hour.

Assuming that the length of step of the average man is 30 inches, the following rate-of-march table is deduced:

+ + -+ Miles Steps per minute per hour + + -+ 35 (1/5) 1 70 2 88 (in practice, 90) 2-1/2 97 (in practice, 100) 2-3/4 106 (in practice, 110) 3 + + -+

[Note. By remembering that 35 (1/5) steps per minute gives 1 mile per hour, the number of steps per minute necessary to give a rate of 2, 2-1/2, 2-3/4 and 3 miles per hour, is quickly and easily obtained by multiplying 35 (1/5) by these numbers.]

In hot, sultry weather, with the men carrying the full pack, the rate of march would naturally be considerably less than on a cool day, with the command not carrying the pack. It is most important that these and other considerations affecting the rate of march be constantly borne in mind by the officer in command of the column, who should indicate to the commander of the leading company the number of steps to be taken per minute. In indicating the number of steps to be taken per minute, it should be considered whether the men at the head of the leading company are the average, above the average, or below the average in height. A short man, for example, would probably have to take 100 steps a minute to keep up with a tall man walking at the rate of 90 steps per minute.

1221. Marching capacity. The average marching capacity of Infantry is about 15 miles a day, but in extensive operations, involving large bodies of troops, the average is about 12 miles a day. Small commands of seasoned Infantry marching on good roads in cool weather can average about 20 miles a day.

1222. Halts. A halt of 15 minutes should be made after the first half or three quarters of an hour of marching to enable the men to attend to the calls of nature and adjust their clothing. Judgment must be exercised in selecting the place for this halt; it should not be made in a village or other place where its object would be defeated.

After the first halt a halt of 10 minutes is made in each hour, that is, the troops march 50 minutes and then halt 10. Of course, the number and length of halts should be varied according to the weather, condition of the roads and the equipment carried by the men. In the tropics the best results are often obtained by marching 45 minutes and halting 15.

When the day's march will run well into the afternoon, a halt of about one hour should be made at noon and the men allowed to eat.

Places for long halts should be selected with care; woods, water and shade are desirable features. Arms are stacked and equipments removed.

Halts should not be made in or near towns or villages unless to procure water or supplies, and when so made, the men remain in column, details being sent for whatever is necessary.

In hot weather, especially in the tropics, it may be advisable in the case of long marches to halt for three or four hours during the hottest part of the day and finish the march in the late afternoon or early evening. As a general proposition, however, it is inadvisable to arrive at a strange place after nightfall or even late in the afternoon.

1223. Crossing bridges and fords. When a cause of delay,—for example, a damaged bridge,—is encountered, the troops in rear are notified of the minimum length of the delay; they then conduct themselves as at regular halts.

In ascending or descending slopes, crossing streams or other obstacles, or passing through defiles requiring a reduction of front, every precaution is taken to prevent interruption of the march of the troops in rear. If the distances are not sufficient to prevent check, units are allowed to overlap; if necessary, streams are crossed at two or more places at the same time; in passing through short defiles the pace is accelerated and the exit cleared at once.

If a company unit is delayed while crossing an obstacle, the head slackens the pace or halts until all of that unit has passed; it then resumes its place in the column, increasing the pace, if necessary.

Before attempting to cross with bodies of troops, careful examination is made of fords, boggy places, bridges of doubtful character, ice, etc., as the case may be.

Troops must never cross a bridge in cadence,—that is, the men must not be in step.

In fording a deep stream with a swift current, the men cross on as broad a front as possible, marching abreast and holding hands. They should not look at the water, but at the opposite shore. If the ford is wide enough, mounted troops may cross at the same time on the upstream side, thus breaking the force of the current.

Fords that are at all difficult delay long columns unless the troops cross at several places at once.

1224. Straggling and elongation of column. The marching efficiency of an organization is judged by the amount of straggling and elongation of the column and the condition of the men at the end of the march.

An officer of each company marches in its rear to prevent undue elongation and straggling. If there be only one officer with a company, the first sergeant performs this duty.

No man should leave the ranks without permission. If necessary for a man to fall out on account of sickness, he should be given a permit to do so by the company commander or the officer at the rear of the company. This permit is presented to the surgeon, who will admit him to the ambulance, have him wait for the trains, or follow and rejoin his company at the first halt.