Inmilitary engineering, aditch is an obstacle designed to slow down or break up an attacking force, while atrench is intended to provide cover to the defenders. In military fortifications, the side of a ditch furthest from the enemy and closest to the next line of defence is known as thescarp while the side of a ditch closest to the enemy is known as thecounterscarp.
In early fortifications, ditches were often used in combination withramparts to slow down the enemy whilst defensive fire could be brought to bear from the relative protection afforded by the rampart and possibly thepalisade. Inmedieval fortifications, a ditch was often constructed in front of adefensive wall to hindermining andescalade activities from an attacker. When filled with water, such a defensive ditch is called amoat. However, moats may also be dry.
Star forts designed by military engineers likeVauban, comprised elaborate networks of ditches andparapets, carefully calculated so that thesoil for the raisedearthworks was provided, as nearly as possible, entirely by the excavations whilst also maximising defensivefirepower.
Today ditches are obsolescent as an anti-personnel obstacle, but are still often used as anti-vehicle obstacles (see alsoberm).
A section through the ditch and rampart of a typical early modern artillery fortification (16th to 19th centuries). The elements are: a) glacis, b) banquette, c) covered way or covertway d) counterscarp, e) ditch (dry), f) cunette, g) scarp or escarp, h) faussebraye, i) chemin de ronde, j) rampart (exterior slope), k) parapet, m) terreplein.
Scarp: the inner side of the ditch (closest to the fort) is called the scarp (or escarp) slope. This may berevetted with masonry or brickwork, in which case, it is called the "scarp wall".
Cordon: a course of protruding masonry along the top of a scarp wall, intended to make it harder for an enemy to stand a ladder against it.
Rampart: the actual wall of the fort which can be made of earth or masonry, is topped by a parapet for the defenders to fire over, and usually slopes away from the ditch (the "exterior slope").
Berm: a ledge between the scarp wall and the exterior slope of the rampart, designed to increase the stability of the rampart and prevent any falling debris from compromising the ditch.
Faussebraye: a secondary parapet between the rampart and the inner edge of the ditch.[1]
Carnot wall: aloopholed wall between the rampart and the inner edge of the ditch.
Chemin de ronde: a pathway running along the berm, behind the faussebraye or Carnot wall.[2]
Cunette: a narrow channel that runs along the floor of the ditch for drainage purposes.
Bartardeau: a type of masonrydam across a ditch that is part wet and part dry.[3]
Counterscarp: the outer slope or wall of the ditch (furthest from the fort).
Sally port: a small door allowing the defenders to enter the ditch should it be occupied by the enemy.
Caponier: a masonry or brick structure extending into the ditch or traversing across it; it is pierced with loopholes to enable the defenders to fire along the floor of the ditch.
Counterscarp gallery: a passage constructed behind the counterscarp wall and pierced with loopholes, which enables the defenders to fire on attackers who have entered the ditch.
Glacis: an earth slope angled away from the ditch; the height and angle of the glacis was calculated to protect the rampart from direct fire, and to allow the defenders to shoot over it.
Covered way: a path running between the outer edge of the ditch and the glacis, allowing defending troops to move around the exterior of the fort; it was usually provided with abanquette orfire step so that defenders could shoot over the crest of the glacis.
Place-of-arms: an open area of the covered way at an angle of the ditch, where defenders could assemble for a sally orcounter attack.[2]
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