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. Cla.s.sification.= Field fortifications are usually divided into three cla.s.ses, =hasty intrenchments=, =deliberate intrenchments= and =siege works=.

=Nomenclature of the Trench.= The following ill.u.s.tration shows the names of the various parts of the trench.

[Ill.u.s.tration: Fig. 1]

=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.

[Ill.u.s.tration: Fig. 2]

[Ill.u.s.tration: Fig. 2a

_Intrenching under fire_]

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.

[Ill.u.s.tration: Fig. 3]

=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 pa.s.sage 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.

[Ill.u.s.tration: Fig. 4]

[Ill.u.s.tration: Fig. 5]

[Ill.u.s.tration: Fig. 6

Simple Standing Trench, Parapet Suppressed]

[Ill.u.s.tration: Fig. 7

Simple Standing Trench, Rocky Ground]

[Ill.u.s.tration: Fig. 8

Narrow Firing Trench with Parados]

=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 pa.s.s 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 pa.s.sage 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.

[Ill.u.s.tration: Fig. 9]

[Ill.u.s.tration: Fig. 10]

[Ill.u.s.tration: Fig. 11]

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.

[Ill.u.s.tration: Fig. 12]

[Ill.u.s.tration: Fig. 13]

[Ill.u.s.tration: Fig. 14

Protection against Shrapnel]

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 pa.s.sage or from trenches dug as far as 5 or 10 feet in front of the main excavation and reached by short pa.s.sages. Figs 15 and 16 show the type of this construction. Fig. 17 shows a fire trench with parades and shelter.

[Ill.u.s.tration: Fig. 15

Two Methods for Communication Trenches in rear of Firing Trenches]

[Ill.u.s.tration: Fig. 16

Communication Trenches in rear of Firing Trenches

Recessed and Traversed Firing Trench]

[Ill.u.s.tration: Fig. 17

Trench 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 sh.e.l.ls, 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).

[Ill.u.s.tration: Fig. 18

_Store Recesses for Water, Hand-Grenades, Reserve Ammunition, Machine Guns, Range Finders, Blankets, etc._ (From _Field Entrenchments_--Solano.)]

=1151. Parados.= Instead of shrapnel, explosive sh.e.l.l 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.

[Ill.u.s.tration: Fig. 19]