Field Trenches

The next element of the defensive position is the first line fire trenches. These are located so as to have a good field of fire to the front for several hundred yards and so constructed as to give the greatest cover and protection from the fire of the enemy.

An unbroken, continuous trench would be exposed to enfilade fire. A shell, shrapnel or grenade bursting therein would have widespread effect. To overcome these elements the trench is constructed in short lengths, with traverses between them, and technically known as the traverse type.

Better defilade is thus secured and the material effect of any burst is confined to narrow limits.

The trench interval between the traverses is known as the "bay," which should not ordinarily be longer than 18 feet. Longer bays invite heavy casualties in case the trench is enfiladed or a high explosive shell finds its mark.

The illustration, Plate 14, shows a trace of the traversed type of fire trench.

Type of Trench

Formerly, protection from the enemy's fire was obtained by thickness of parapet. In the trench warfare of today it is obtained by completely concealing the riflemen in a deep, narrow trench with a very low parapet.

The height over which the average man can fire is about 5 feet or about five-sixths of his own height. This factor determines the height of the parapet above the firing banquet of the trench or the height of bottom of loophole above the same point, when the latter is employed.

The type of trench in general use today is the simple standing trench shown in Plate 15.

Drainage

If a trench is to be occupied for any length of time, especially if much ground or falling water is to be encountered, drainage becomes of prime importance. Many years ago a celebrated military authority asserted that "nothing so saps the courage of a soldier as to wet the seat of his breeches." This may be accepted as a true maxim, especially in cold weather. The trench should therefore be made as dry as possible. The floor of the trench should be given a sufficient slope to the rear where an intercepting drain should carry the water to prepared sumps or to a point from which it can be disposed of by drainage. Provision should also be made to exclude surface drainage from the trenches.

A scheme for trench drainage is shown in the illustrations (Plates 16, 17 and 18).

Overhead cover may be provided as shown in Plates 19 and 20.

Loopholes are made wherever head cover is provided. Where the enemy's trenches are close, there is considerable danger in using them. Collective firing takes place over the parapet. When loopholes are used they should face half-right or half-left and not directly to the front.

The disadvantages of loopholes are:

1. The difficulty of concealing firing points. Loopholes give the enemy's snipers an easy mark.

2. They lessen the number of rifles that can be used at a given point.

3. The necessary head cover makes it difficult to get out of the trench quickly.

4. Damaged head cover often spoils a good firing point.

The three types of loopholes are:

1. Narrowest point of the opening nearest the marksman. This type is most difficult to conceal, much of the parapet thickness is cut away and, if of hard material, tends to deflect the bullets into the firer's face. This defect may be remedied somewhat by stepping the surface of the loophole.

2. Narrowest point to the front. Easiest to conceal but gives a limited field of view.

3. Narrowest point midway between the front and rear. A compromise between the first two types.

The following general remarks on the construction of loopholes are taken from a work based upon the experience gained during the war in Europe:

1. The angle of splay is usually 60 degrees. The thicker the parapet the smaller must be the angle of splay.

2. The marksman holds his rifle in a line connecting the right shoulder, the eye and the object, hence most of the body lies to the left of the rifle. The loophole should be made to the
right, with a niche in the wall of the parapet from the hip to the armpit, to bring the left shoulder well forward. It will be found that this permits the right elbow to be placed on the edge of the parapet.

3. Box loopholes with screens or blindage may be used, but should be placed by a skilled marksman. The great disadvantage is that the enemy notes these parapet alterations. Steel loophole plates are now provided for this type of loophole, As the Germans sometimes use a steel bullet with great penetrating power, it is advisable to place two plates together to insure protection.

4. With every precaution that may be taken it is difficult to conceal a loophole. A good plan is to deceive the enemy by using painted sandbags and preparing plenty of dummy loopholes.

5. The minimum width of loopholes should be 2-1/2 inches. If narrower than this, it is impossible to use both eyes to judge distances correctly.

6. The parapet should be so sloped that there is a maximum grazing fire when the rifle is fired as it lies on the parapet.

To insure that the bullet will not graze the parapet, although the sights are clear, look through the barrel with the bolt removed.

In the first line fire trenches there are so many crooks and turns and the trench itself is so narrow that passage along the same is very difficult. To provide for this lateral communication a trench known as the communication or supervision trench is dug. It runs generally parallel to and a short distance in rear of the fire trench and is connected therewith by zigzag approaches. The factor that determines the distance between the fire trench and the communication trench is that it should be at such a distance that a shell bursting in one of the bays would not destroy the communication trench.

The location of the communication trench with respect to the fire trench and the arrangements of the approaches is shown in detail in Plate 1.

The profile of the ordinary communication trench is shown in Plate 23.

During the artillery bombardment few men are left in the fire trenches. The remainder of the garrison is held under cover a short distance to the rear. This cover is provided by a system of dugouts connected with the fire trench through underground passageways that lead to the communication trench. This arrangement is shown in Plate 1.

A profile of the latest type of dugout is shown in Plate 24.

The solid earth cover is from 12 to 18 feet thick, which gives protection from all but the very largest caliber shells.

Effective resistance is supplied by roofing materials as follows:

1. From shrapnel bullets: 2-inch planks covered with 12 inches of earth.

2. From 3-inch shells: 4-inch planks supporting 4 feet of earth with a top layer of heavy stones to cause an early shell burst.