Rifle pits—as the term is now generally used—are small embankments, made by throwing up dirt from an excavation inside. They can be erected quickly, for it will be seen that those behind them have the advantage, not only of the height of the embankment, but also of the depth of the ditch. Thus an excavation of two feet would give a protection of four feet. This is the ordinary rifle pit, but when time permits it receives many improvements.
Breastworks are any erections of logs, dirt, etc., raised breast high, to shelter the men behind them.
An abatis consists of obstructions placed in front of a work to form obstacles to a storming party. The most convenient method of forming it is to cut down trees and allow them to lie helterskelter. When there is time, the trees are laid with the butts toward the work, and the branches outward—the small limbs being removed, and the ends of the remainder sharpened.
A redan is a letter V, with the point toward the enemy, and is used generally to cover the heads of bridges, etc.
A lunette is the redan with flanking wings.
A redoubt is an enclosed parallelogram.
These works are very imperfect, because they have exposed points. The angles are not protected by the fire from the sides. To remedy this difficulty, the next most usual work is the star fort, made in the form of a regular or irregular star. It will be perceived that the fire from the sides covers the angles.
The next and still more improved form of work is the bastioned fort, which consists of projecting bastions at the corners, the fire from which enfilades the ditches.
The following is a diagram of a vertical section of the parapet and ditch used in all fully constructed field works:
