A military dictionary

by William Duane

The trenches are usually opened or begun in the night time, sometimes within musquet shot, and sometimes within half or whole cannon shot of the place; generally about 800 toises. They are carried on in winding lines, nearly parallel to the works, so as not to be in view of the enemy, nor exposed to the enemy’s shot.

The workmen employed in the trenches are always supported by a number of troops to defend them against the sallies of the besieged. The pioneers, and other workmen, sometimes work on their knees, and are usually covered with mantlets or saucissons; and the troops who support them lie flat on their faces, in order to avoid the enemy’s shot. On the angles or sides of the trench, there are lodgments, or epaulements, in form of traverses, the better to hinder the sallies of the garrison, and to favor the advancement of the trenches, and to sustain the workmen.

The platforms for the batteries are made behind the trenches; the first at a good distance, to be used only against the sallies of the garrison. As the approaches advance, the batteries are brought nearer, to ruin the defences of the place, and dismount the artillery of the besieged. The breach batteries are made when the trenches are advanced near the covert-way.

If there are two attacks, it will be necessary to have lines of communication, or boyaus, between the two, with places of arms at convenient distances. The trenches are 6 or 7 feet high with the parapet, which is 5 feet thick, with banquettes for the soldiers to mount upon.

The approaches at a siege are generally carried on upon the capitals of the works attacked; because the capitals produced are, of all other situations in the front of a work, the least exposed to the fire of either the cannon or musquetry; and are the least in the line of fire between the besieged and besieger’s batteries. But if, from particular circumstances, these or other advantages do not attend the approaches upon the capitals, they are by no means to be preferred to other positions.

The trenches of communication, or zig-zags, are 3 feet deep, 10 feet wide at bottom, and 13 feet at top, having a berm of one foot, beyond which the earth is thrown to form a parapet.

The parallels or places of arms of the trenches are 3 feet deep, 12 feet wide at bottom, and 17 or 18 feet wide at top, having a banquette of about 3 feet wide, with a slope of nearly as much. See [Sap].

The first night of opening the trenches, the greatest exertions are made to take advantage of the enemy’s ignorance as to the side of attack; and they are generally carried on as far in advance as the first parallel, and even sometimes to the completion of that work. The workmen set out on this duty, each with a fascine of 6 feet, a pick axe, and a shovel; and the fascines being laid so as to lap one foot over each other, leave 5 feet of trench for each man to dig.

The usual method of directing the trenches or zig-zags is, by observing during the day some near object in a line with the salient parts of the work, and which may serve as a direction in the night; or if the night be not very dark, the angles of the works may be seen above the horizon; but as both these methods are subject to uncertainty, the following is proposed to answer every case:—Having laid down the plan of attack, the exact positions of the flanked angles of the works of the front attacked, and particularly of those most extended to the right and left; marked on the plan the point of commencement for the first portions of zig-zag, the point where it crosses the capital, 2nd the point to which it extends on the other side of the capital: this last point will be the commencement of the second branch: then mark off the point where this branch crosses the capital, and its extent on the other side; and this will give the commencement of the third branch; and so on for the others. Thus provided with a plan ready marked off, it will be very easy, even in the darkest night, to lay down the points where the zig-zags are to cross the capital, and the points to which they are to be produced beyond them. The first parallel is generally run about 600 yards from the place, and of such extent as to embrace the prolongation of the faces of all the works which fire upon the trenches; and each end has a return of about 30 or 40 yards.

The second parallel is constructed upon the same principles, and of the same extent as the first, at the distance of about 300 yards from the salient angles of the covert-way. This parallel is usually formed of gabions; each workman carrying a gabion, a fascine, a shovel, and a pick axe. After this the trenches are carried on by sap.