Chapter XI: Field Engineering

(_See also_ “Manual of Field Engineering.”)

=238.= _Entrenching and concealing guns._

1. The importance of concealment, both in attack and defence, has increased with the destructive effect of quick firing artillery, but is valuable only so long as its employment does not interfere with effective fire.

2. There is a two-fold object in making use of cover, viz., concealment from view and protection from fire. By these means the possibility of surprising the enemy with fire is increased, while the possibility of being immobilized by hostile fire is diminished.

3. Guns may be concealed either by making use of natural or artificial cover, and sometimes by the selection of sites with a suitable background, but reconnaissance of the position can alone show if concealment is likely to be temporary or permanent. If circumstances permit, the sites for the guns should be viewed from the most suitable observation posts for the enemy’s artillery before they are finally fixed, bearing in mind that positions which are effectively hidden from the front often become visible by moving a short distance to a flank.

4. Advantage should invariably be taken of any natural cover available, but to give efficient protection against fire some artificial cover will usually be required.

When the contour of the ground is favourable trees will give valuable cover from view, and so make it more difficult for the enemy to obtain the range. A position behind a wood, a hedge or belt of trees can often be found where the guns can be brought into action unseen by the enemy, the fire being observed from a position in rear.

5. Experience shows that anything that breaks the view close in front of distant objects greatly increases the difficulty of seeing them. Such material as nets or bamboo trellis with bits of the surrounding vegetation stuck into them may be used for this purpose. If guns have to be placed on a skyline, a strip of sacking stretched in front of them may serve as a false skyline when viewed from the enemy’s position. Similarly brushwood hurdles placed behind guns to act as a background will often conceal them for the time being.

To prevent guns being located by the dust thrown up on discharge the ground should be watered for some yards in front of the muzzles, or such material as raw hides, and sacking, pegged down over it.

For a similar reason the movements of guns and individuals must be restricted as much as possible when there is any likelihood of the enemy being able to observe them.

6. In entrenching guns the first consideration is fire effect, the second that while getting some cover in the shortest possible time the form of the work should be such as to admit of gradual improvement in the event of more time being available.

The site of a gun emplacement having been selected, the first step is to decide whether an epaulment or pit is most suitable, the next is to mark out the platform for the gun, which must be large enough to enable it to be traversed so as to engage any likely objective.

In deciding whether gun pits or epaulments are to be made, it must be remembered that sinking the guns reduces their field of fire and makes more dead ground in front of them if the position is not already under cover.

On the other hand the difficulty of locating guns from aircraft is greater if sunken sites without parapets are employed.

7. At first, a simple parapet to supplement the cover afforded by the shield and to protect the detachment, when kneeling, from oblique fire should be provided. For this purpose some empty corn sacks may be carried by guns on active service. These may also be found useful in bright weather in preventing the glint from the tyres disclosing their position. Subsequently the cover can be improved and pits, with ammunition shelves or recesses in front or rear to cover the detachment standing, may be added, but a clear space of 13 feet between these pits is necessary for working field guns. The breadth of the embrasure will depend on the field of fire to be covered. The recoil of the gun carriage should be prevented by digging a trench for the spade, butting it against a plank or sleeper.

8. Every effort should be made to assimilate the emplacement with its surroundings. Sharp angles, steep ends and clearly defined embrasures, which throw dark shadows, should be avoided as likely to attract attention, and the intervals between the emplacements themselves may be filled with some form of screen with advantage.

Any newly-turned earth, if liable to be seen by the enemy, should be covered with turf, bushes, &c.

9. If time and tools permit, cover for an ammunition wagon near each gun, and a blinded communication trench for the men replenishing ammunition should be provided; or, where this is not practicable, some shelter pits to afford resting places for the men supplying ammunition by hand from the wagon line.

Where still more time is available traverses against enfilade fire and overhead splinter-proof cover may be prepared. For the latter purpose uprights are needed to carry horizontal transoms on which planks or corrugated iron are arranged to support earth to the thickness of 12 inches. Uprights and transoms should be 8 to 10 inches in diameter, except in the case of such of the latter as are only required for short spans.

Special cover is required for the battery commander and his headquarters, the battery leader and his signallers, and section commanders. A type of protected observing station is shown in Plate IV. If time admits, head cover with some form of loophole should be added.

10. Diagrams of an epaulment and gun pit are shown on Plates V and VI, but they are not intended as types to be rigidly copied on all occasions.

For heavy guns a parapet about 3 feet in height should be carried round in front of the carriage, and should be constructed with a radius admitting of ample interior space and a wide field of fire. The gun should be run as close to the parapet as possible. It is generally inadvisable, unless artificial platforms are available, to disturb the natural surface of the ground.

11. Cover from both view and fire may sometimes be obtained by a combination of natural and artificial cover:--

i. By scarping the reverse crest of a steep ridge
(_See_ Fig. 34).

ii. By sinking pits close to the front crest of a feature
(_See_ Fig. 35).

PROTECTED OBSERVING STATION.]

GUN EPAULMENT FOR SHIELDED GUN.

(_Not drawn to Scale._)

The breadth of the embrasure must depend on circumstances; if the field of fire is limited by ground or by the target it can be narrowed, if not it must be fairly broad.]

GUN PIT FOR SHIELDED GUN.

(_Not drawn to Scale._)

The breadth of the embrasure must depend on circumstances; if the field of fire is limited by ground or by the target it can be narrowed, if not it must be fairly broad.]

12. In some circumstances guns may have to be entrenched under cover of darkness in readiness to open fire at daylight. Careful preliminary reconnaissance is the chief essential to avoid mistakes in carrying out the various works (_See_ Sec. =189=), special care being taken to make sure that the principal line of fire is laid out correctly.

While the nature of the soil, the proximity of the enemy and the time available will all have their influence on the details of the works, every endeavour should be made to conceal them from view.

=239.= _Passage of obstacles._

1. The obstacles likely to be met with will vary from walls or ditches to unfordable rivers. In the case of the smaller obstacles a few minutes’ use of the tools carried with the battery will often be all that is required.

2. Obstacles should be crossed at right angles and in column of route, as each carriage will make the way easier for the one which follows. In the case of boggy places, however, each carriage should cross at a different spot. The gunners should always be dismounted from the carriages if there is any likelihood of the latter being overturned.

3. For the passage of small ravines a serviceable bridge can be quickly made by using a pair of wheels on their axle to support the road-bearers. _See_ Fig. 36.

If the bottom of the ravine is soft, two spars, D and E, should be lashed to the wheels as shown. The wheels are then lowered, hauled into position, and secured by guys AB, BC.

One or two transoms (H) are then lashed across the top of the wheels with square lashing and the road-bearers (R, R) placed in position. The number of the latter depends on their strength and on the weight to be passed over.

Transoms 4 × 9 inches (8 inches in mean diameter if round) and 5 road-bearers, mean diameter 6½ inches, will bear field guns and howitzers. The road-bearers should be butted against pieces of timber (F, G) sunk in the ground.

If planks are procurable to form the roadway, they should be used. If not, the road-bearers must be placed close together and covered with branches of trees and brushwood. If horses are to cross the bridge, it should be covered with earth to deaden the sound.

4. Plate VII shows another type of bridge constructed with stores, most of which are carried with a battery.

5. Should it be required to pass field guns across a river quickly, the gun and carriage can be floated across by means of four casks lashed as shown in Plate VIII.

The number of casks required can be calculated from the following rule:--

The available buoyancy of a cask (_i.e._, weight which it will support) in pounds is found by multiplying its contents in gallons by 9. Thus a 108-gallon cask has an available buoyancy of 972 lbs.