Part 3

CORRUGATED IRON. Generally, when lengths of corrugated iron and plenty of floor boards and stakes are available, this material is used for revetting the lower half of a trench wall, as it removes a great many difficulties, such as looking over substantial foundations for sandbag revetments. It makes it unnecessary to fill sandbags, etc., thus saving a great amount of time and labor. In revetting with corrugated iron and stakes or hurdles, cut the slope or wall from 10 to 15 degrees from the perpendicular, putting the soil in the sandbags and leaving it in some handy place for any future use. Then, drive 6´ to 8´ stakes well into the trench foundation and approximately 4´ apart, thus giving adequate protection to each piece of corrugated, having the stakes at an angle of 15 degrees at least, from the perpendicular, and 6″ or 8″ away from the trench wall. Then, slide the corrugated, hurdles, or boards on their sides down behind the stakes, overlapping slightly the ends and ramming them well down into the mud or soil in the bottom, and filling in the space behind with soil.

The bottom third or half of the front wall is thus substantially, easily and quickly revetted, and the upper half or remainder is generally revetted with the sandbags, a bed being dug so that the first layer of headers is about half its depth below the top of the corrugated. If stakes shorter than 6´ or 8´ have been used in the revetting, half should be cut off to where the sandbag revetting commences and wired to anchor stakes, driven into the parapet end of the bed, and not wired over the top of the parapet, as it tends to gradually pull them upwards. Then cover this wiring with your first layer of headers. When hurdles or floorboards are used instead of corrugated iron, empty sandbags or similar material must be hung behind them to prevent the soil crumbling through and thus weakening the foundation of the sandbag revetments. Corrugated should not be used for revetting the front wall higher than 2´, which is the width of one sheet, as the supply is generally limited and can be put to more valuable use as dealt with later.

Corrugated iron comes in bundles of about 24 sheets to the bundle, averaging 6´ by 3´. Two sheets is the average load for any one man in a carrying party.

A front wall constructed in the manner shown, if prompt and immediate attention always be given to repair if damage is done, will give very little bother. It is the usual custom to construct your fire platform after this revetting work has been done.

A trench should be dug no deeper than will afford protection to the firer, a deeper passageway necessitating a fire platform, a subsequent work, and by first revetting the whole front wall from bottom to top then adding the fire platform, each gets the benefit of the foundation of the other. Until this fire platform is constructed, emergency methods may be used and improvised in a moment with ammunition boxes, loose sandbags and the various other junk which accumulates in a trench.

FIRE PLATFORMS. Now that the front wall has been revetted, either with corrugated or sandbags, the construction of the fire platform should be at once started. To start this, short stakes should be driven well into the trench bottom about 36″ from the front wall and parallel to the slope of the front wall, averaging from 2´ to 3´ apart and generally as substantial as the large revetment stakes, although this is not of absolute necessity.

When brushwood is procurable, it should be used as a foundation, putting it in after the short stakes are driven and ramming it down behind them. This gives you as nearly as possible a dry and compact foundation for your first row of headers. Then this may be covered with another lot of brushwood, and that again by a row of headers, and from then the layer should be alternate headers and stretchers. Sand bags do not offer a good platform after a heavy rain, as they become wet and slippery and the material quickly rots, then they break open and the top of your fire platform is gone. To avoid this, it is necessary to use whatever material may be at hand in the covering of the top layer.

One good way of providing this top covering when the material is procurable, is a wire netting used in a double thickness. It should be placed behind and up against the stakes before the foundation is laid. Then when the fire platform is built to its proper height, bend the wire from the top of the fire platform and fasten it down on the sides by whatever means are handy. Using this double wire netting makes it possible to use brick and all sorts of general trash in the construction of the fire platform and gives a very good dry footing. When doing that the face of your platform should be either corrugated sheets or boards.

Very often what are known as sentry-boards, or small floor boards about 36″ square and with additional cross pieces underneath, giving them a height of about a foot, thus raising them well out of the mud, are used, and are very handy before a fire platform is made, and in some cases have to be used for small men after the fire platform is made.

TRAVERSES

All the walls of the traverses must also be revetted, generally with the sandbags and in exactly the same manner as the front walls of a fire-bay, care being taken to keep it well sloped. This leads to a lessening of protection afforded the occupants by making a greater width at the top of the trench, but it is absolutely necessary unless you wish your whole traverse to gradually fall in, when you are in a position of having no protection at all. The top of the traverse may be and is often several feet higher than the parapet, if the fire-bay it protects is exposed to enfilade fire from the enemy trench at a higher level. But when this is not the case, the traverse should not be higher than the parapet or parados, and should slope down towards the enemy to give the appearance of being merely a continuation of the parapet.

The traverse should never be less than 9´ wide, allowing 2´ for a sentry box, although this sentry box is no longer generally in use.

What are known as overhead traverses are made generally in a communication trench leading up to the front line, and which in certain parts the enemy are able to look into. These overhead traverses give to this particular place the protection which is necessary. They are quickly and easily made by placing corrugated iron, logs or strong branches, or floor boards, across the top of the trench and putting sand bags on the top of these. When the trench walls are weak, or even on general principles, the sides supporting this overhead traverse should be revetted with sandbags.

The sentry boxes, although not in general use now, are described, more for general information than anything else. They are dug or recessed in the traverse at either end of the fire-bay and must have an observation slit in the parapet for use by day, but no loophole facing the enemy, as regardless of the care and caution used in the construction of these loopholes, they will sooner or later, generally sooner, be observed by the enemy and the sentry box made useless.

During an attack this sentry box is never used, except for stores or the placing of wounded, as there will always be plenty of room for the late occupant in the fire-bay itself. Sometimes, when energy and time permit, an enfilade fire loophole is made through the traverse and facing the next fire-bay, but this has as much value for making easy verbal communication from one fire-bay to another as it has to the checking of attacking forces.

LISTENING POSTS

As before mentioned, in the space between the front lines of the opposing armies, which is known as No Man’s Land, there are sometimes large and sometimes small areas of ground, ditches, streams, etc., which cannot be satisfactorily watched from a fire trench immediately facing them, owing to the lay of the land, hedges, old excavations, buildings, etc. This is the case in a great many instances regardless of the careful thought and the amount of time spent in siting a fire-trench, as the siting of all trenches is largely subsidized by the tactical position of the flank trenches. Very often a line of trenches is taken up under stress of circumstances that do not permit of the obeying of the rules and standards set for an ideal fire-trench.

The control of these areas is essential to prevent small surprise attacks, cutting-out parties and raids. During the day they are very often observable from a flank trench or higher observation ground in the rear, but at night this is not possible; so that listening or observation posts are gradually sited in front of the fire trench with due consideration to the situation in that immediate vicinity. A ruined shed, shack, cart, or any other thing of a similar character lying in No Man’s Land is very useful for these purposes if it can be reached before the enemy reach it with the same purpose in mind. This cannot be used very long, as its purpose is too obvious and peace and quietness will not last long, but it will do until a more satisfactory arrangement can be made.

The listening post is often dug just inside the outer fringe of your own barbed wire entanglements, and is just large enough to allow two men to stand in unobserved. It should be reached by a very narrow, irregular trench running out from a fire-bay, where it is fairly easy to secure the maximum amount of concealment necessary to give protection. The soil excavated from these places must not be thrown out, but placed in sand bags and taken into the trench and used there. It is always best and requires very little more labor, and gives the maximum amount of protection to your listening post if communication to it be made through a tunnel.

These things are bound to be discovered within a certain amount of time, and when you know the position of your listening post has been found by the enemy, which you will know very quickly, owing to the amount of bombs and rifle fire it will receive for one or two nights, until you can dig another one, it is a safe thing to build up a small parapet, taking it down every morning before dawn. It then becomes necessary to dig a new post, and this can be generally done by leading off from your old communication trench to some more favorable spot. When the new post is ready for occupancy, the old one should be filled in with barbed wire, or completely filled in again with dirt, and the sandbag parapet left to mislead as long as possible.

The first duty of a listening post is to listen and report. Most of the work is done at night, and no firing or sniping must be allowed from it during the day. Patrols generally come out via one listening post and return by another, so that all listening posts must be warned of the trench by which the patrol will come out and the approximate hour of departure and return. Patrols should never be sent out without definite orders as to what is required, and especially as to the listening post they leave and return by. Listening posts should fire without challenge at any one who approaches within sight, whether friend or enemy, unless it has been warned that a friendly patrol is out, in which event signals should be pre-arranged. Then the listening post will use the greatest caution and should challenge audibly when the patrol is close, and unless immediately satisfied, fire. Listening posts are connected with the fire trench by a cord or wire, and a simple code of tugs is arranged, or a bell fastened to the fire trench end for alarm in case of emergency, and here a sentry always stands to get any signals that may come from the listening post.

If a listening post has not been warned that a friendly patrol is out and fires on it without challenge, the L. P. is absolved from all blame.

When a hedge or ditch, which might easily provide cover to the enemy, is running parallel with the firing trench, it must be controlled at night by a machine or Lewis gun which is able to enfilade a frontal advance over open ground leading to it. If, as is often the case, the parallel hedge or ditch is easily approached along either hedges or ditches running at right angles to it, these angles must be protected by machine or Lewis gun firing down them.

When hedges or ditches running at right angles from the firing line and leading towards the enemy are in a sector of line, they should be protected from dusk to dawn by one or two men, generally only armed with bombs to protect against surprise, and great care must be taken that no more signs than possible are left to the occupancy of this position over night.

OBSERVATION POSTS

LOOPHOLES FOR FIRING. During an attack, firing is never possible through loopholes as it is too restricted to be of any value. All the firing then is done over the parapet. The difficulty of constructing new observation posts which are effectual and inconspicuous for any length of time has resulted in their not being made in a parapet, where, when located by the enemy, they are as often as not a source of danger. Moreover, promiscuous firing through loopholes by inefficient riflemen is of no value. Sniping is under the control and supervision of a sniping officer, and loopholes should only be used by men appointed by that officer. They are not used at night and should be only used during the day for enfilade fire, and be placed in the parapet as low down as is consistent with line of site. A piece of cloth or empty sandbag should be hung from the rear of the loophole, so that when the hole is not obstructed by the fire, no light can show through. No shots should be fired from those loopholes, except at a definite target, and ranges of targets or spots where targets may possibly appear, should be ascertained in advance, and necessary exposed movement, such as withdrawal of rifle, must be very slow and gradual. With care, and when only used by a skilled rifleman, a loophole will be of value for probably two weeks and good results obtained, but by a careless man the value of a loophole will not last a day and very likely result in casualties not only to the man shooting, but to others as well.

In the area from 20 to 100 yards behind the fire trench, there sometimes is, although very seldom, ground much higher than the actual fire trench, so that it is safe to allow even hastily trained men to use it for firing over the heads of the main front line trench, although it has happened that men in such a position have fired into their front line, thinking it the enemy line. This ground is generally used by building what are known as covering fire trenches. These to be of any value, should not be more than 20 yards behind the front line, as farther forward than 20 yards they become affected by artillery fire directed at the fire trenches; and farther back than 100 yards the covering fire, unless in the hands of very skilled and efficient riflemen, becomes very dangerous to the men in the front line.

SUPPORT TRENCHES AND SUPPORT DUGOUTS

A support trench is usually within 30 to 300 yards of a fire trench, and may serve the purposes of covering fire trenches by skilled riflemen or an indirect machine gun fire, but their main purpose is to shelter troops from observation and shell fire, and thus their main characteristics become the size and strength of ample dugouts. Troops in the support dugouts are at hand for three purposes: Firstly, replacing of casualties occurring in the fire trenches during normal times or a hostile attack. Secondly, holding the support trenches in case the fire trenches are taken by the enemy. Thirdly, in the event of an attack on the enemy’s trenches, leading the attack by moving forward over the heads of the occupants of the fire trench, or if the latter are leading the attack, to occupy at once the fire trench when vacated. For this reason it is of vast importance that there are accessible and commodious support dugouts and communications between the immediate support trenches and front line. If this is so there will be less chance of disasters to supports and reserves coming up to make good a successful attack. There must be support dugouts even in the event of there being no support trenches, and this is very often possible owing to the lay of the land. The strength and size of these dugouts entirely depend on tactical considerations and local conditions, which are generally decided by the staff.

SUPPORT POINTS

These forts or strong points, as they are sometimes called, usually round or square, but which may be any shape best suited to the condition of the country in which they are placed, are generally from 100 to 300 yards behind the fire-trenches and supplementary to the support trenches. Each of these strong points contains a permanent garrison of firing troops, strongly protected with barbed wiring and sandbag revetments, and well supplied with ammunition, food and water, to enable them to withstand heavy attacks. During an attack they are used to give overhead covering fire, and for the control of ammunition and other supplies to be sent on to the firing line. It is a general rule that if the enemy take a fire line the garrison of these supporting points must hold out and remain a thorn in the enemy’s side until the last man of the garrison is killed.

RESERVE DUGOUTS

These dugouts protect the local reserves from which supports are supplied and are used for purposes similar to those for which the immediate support dugouts are employed, but on a great deal larger scale. These dugouts are generally near battalion headquarters and from 500 to 1,500 yards behind the firing line. The chief considerations in siting the positions of these dugouts are three: First: facilities for rapid and easy transit to the support and fire-trenches; second: concealment; third: comfort. Comfort should be secondary to the other conditions affecting the siting of the system.

SECOND LINE

This comprises the line of fire-trenches, with covering fire-trenches, support trenches, support dugouts and reserve dugouts (in other words, it is an exact duplication of the front line system), far enough behind the front line that in the event of the first system being taken, the second line is ready to be taken up by the troops driven out of the front line, and receive the support of troops lying in brigade or divisional reserve. The distance of the second line behind the first is roughly a mile, and while the first line is held, operations of the second often provide useful accommodation for the machine guns and artillery, both for firing purposes, observation and shelter.

The time available for siting and constructing second line system, and the freedom from all disturbances which bother the front line system, should result in its being impregnable. It is an ideal system provided those responsible for its siting and construction are thoroughly and practically experienced with first line conditions and profit by that experience and former mistakes.

COMMUNICATION TRENCHES

When siting communication trenches, two considerations come into conflict with one another; the desire for protection, and the necessity of rapid and easy transit. It is obvious that a C. T. is of vital importance to the firing line in the getting up of supporting troops, ammunition and stores rapidly and without undue fatigue. It is also obvious that it must give as much protection as possible to the troops using the C. T., but it must be recognized that the protection given must not interfere with rapid transit by making the C. T. too narrow. It must also be kept in mind that rapid transit in itself gives a certain amount of protection for the simple reason that the easier and quicker the transit, the less time are troops delayed in the C. T.’s in which protection is required, and if troops can cover the danger area in 10 minutes, they are plainly in danger for a less period than if it took 30 minutes to struggle over that same area. This rapid transit, only obtained by a dangerously wide communication trench from support or reserve lines and from dugouts, also makes it possible for less troops to be regularly on duty in the fire-trenches, which are always uncomfortable and dangerous, especially during a bombardment, and it also enables supports and reserves to be rushed up quickly when the occasion demands.

It can be plainly seen now that a compromise must be effected between claims of protection and rapid transit, so that the size and shape of the C. T.’s will vary according to their distance from a danger area. Generally speaking, the nearer to danger, the more must the claims of rapid transit give way to those of protection.

Disregarding for the time being the claims of protection and only considering rapid transit, there are these things to be considered: First, that a C. T. be as short as possible, making use of contours, sunken roads and other natural features to avoid digging as much as possible. Second, that a C. T. be as straight as possible, which not only shortens the distance but avoids turns and corners which interfere with speed and which require renewed effort at every turn. These sharp corners and turns must always be avoided. This can be done without weakening a trench or increasing the risk, and every effort should be made to save troops carrying full equipment, stores, ammunition, or rations from unnecessary tiring, hindrances, and difficulties, such as sharp corners and turns. Third, the C. T. J.’s must be as level as possible, as they are generally slippery, and inclines or declines should be avoided as they very often cause accidents. A longer C. T. following around natural contours is frequently more advantageous for this reason than a straight one over a hill, which it is only possible to make level by an amount of digging out of proportion to the result gained. The C. T. must be wide enough for requirements. These differ according (a) to the proximity of C. T. to the fire-trenches, (b) to the number of C. T.’s available, and (c) to the use for which a C. T. is required, i. e., whether a double C. T. (for both up and down traffic) or a single C. T. (for traffic in one direction only).

When a C. T. is close to the fire-trench, troops moving into it are practically themselves in the fire-trench and as each group has probably to get to a different part of that fire-trench, all necessary traffic up and down the fire-trench and disturbance of the men occupying it must be avoided. Rapid transit can advantageously be obtained by other means than the width of the C. T.; by dividing the single C. T. at some point from 30 to 60 yards in rear of the actual fire-trench into a number of small narrow C. T.’s, each leading to a group of 3 to 6 fire-bays, and these may again be divided into those for up and those for down traffic.

This system requires a fair amount of thinking out and all the trenches should be plainly marked and named. These names are placed on notice boards at the different junctions having the proper indications and rules directing the use of up and down traffic. This is and should be rigidly enforced during both quiet and active periods, but takes on a much greater importance during active periods.

The width of these single C. T.’s running close to the fire-trenches should be enough to allow a man carrying full equipment, stores, or rations to pass along easily and without bumping the sides with his equipment or burden; approximately two feet at the bottom with ample room at all corners. The width of a single C. T. for down traffic only should be wide enough to allow for passage of a laden stretcher, especially at the corners, as a stretcher is a very clumsy thing to get around these corners and often the delay caused has very serious consequences.