Glossary
Military Earthworks Terms

Gabion - a large basket of interwoven vines and saplings used to strengthen or shape an earthwork.  The gabion was set into position, then filled with earth on site.  When gabions deteriorated, the fill collapsed into shapeless mounds that can sometimes be identified in the field.

Glacis (Fr.) - outer edge of the ditch, or, by extension, the field of fire of a fortification.  In permanent fortifications, the glacis was shaped so that the ground rose gently as it approached the ditch to protect and conceal the masonry revetment of the scarp.  In fieldworks, time permitting, the glacis was sloped as a continuation of the angle of the superior slope of the parapet.  Some surviving artillery works have a shaped glacis, though it is fairly rare.

Gorge - entrance to a detached work, or simply the rear of the work, as in, a lunette is open "at the gorge."  Leaving the rear of a work open allowed defenders in a secondary line to fire into it in case it were captured.  A wooden stockade was sometimes built to close off the gorge.

Grade - original ground level.  Ditch is below grade; parapet is above grade.

Greater or Major Fieldworks - earthworks constructed with an exterior or front-ditch.

Gun Pit - an entrenched artillery position, a platform, demilune or epaulement.

Gun Platform - a flat, usually rectangular, area behind a parapet on which an artillery piece was positioned.  The platform surface was usually floored with planks or split logs or corduroyed with logs placed side by side.  A platform might be excavated or elevated relative to grade, depending on whether it was firing through an embrasure or over the parapet (en barbette).  The size of the platform is indicative of the size of cannon it was intended to service (average 10 x 14 ft. for a standard field piece).  Sometimes, a platform was edged by a narrow drainage ditch or flanked by traverses.

Gun Ramp - a ramp constructed to move a cannon into firing position on its platform; the ramp may ascend or descend to the platform from ground level.  A gun ramp is a common surviving feature of artillery works.

Hasty Entrenchments - See Rapid Entrenchments.

Holes and Pits -  foxholes and other personal defenses.  Single-man skirmish pits or picket holes (foxholes) were typically about four feet in diameter and 2-3 feet deep with the dirt thrown forward to form a low parapet.  These holes were sometimes enlarged to hold two- or three-man firing teams.  Pickets and skirmishers were deployed from 50-300 yards in advance of the main line of defense at intervals of 5-15 yards.  This regularity of placement is one of the principal indicators used in the field to differentiate a picket or skirmish line from random holes caused by tree-throw.  Interspersed along the skirmish line might be slit trenches, which were short, discontinuous segments of parapet dug to cover 3-5 men.  Fire pits or mess holes might be dug out of the ditch behind the main lines for cooking and sleeping.  "Officer holes" sometimes appear at regular intervals from 5-10 yards behind the main lines, where file closers, usually non-commissioned officers, were stationed to keep the rank and file in line.  See Dugouts and Bunkers.

Hornwork - detached earthwork formed of two adjacent demi-bastions and two long flanks extending to the rear and inclining toward the open gorge.

Hurdle - revetment formed by interlacing vines or saplings through a series of posts set upright against the interior slope of the parapet.

Impoundment or Inundation - flooded ground in front of or within a fortification for defensive purposes.

Improving - continuing to strengthen a system of rapid entrenchments over time.  A simple rifle trench could be improved by widening the parapet, adding traverses, excavating dug outs or fire pits behind the line, or adding supply caches and a covered way to the rear.  Soldiers tended to work on their entrenchments more or less continuously for as long as they occupied them to make them safer, more comfortable, and more defensible.

Indented Line - See Cremaillière Line.

Infantry Works - earthworks designed for defense by infantrymen.

Interior Slope - rear slope of the parapet, usually nearly vertical to enable the defender to stand against it to fire over the parapet; often faced by a revetment of logs, rails, planks, sod, wickerwork (called hurdles), stones, sandbags, or other available materials.

Internal Works - structures built within a larger earthwork, such as magazines, bombproofs, and traverses.

Irregular Works - See Regular and Irregular Works.

Keep - a blockhouse or redoubt built within a larger fort for use as a place of final refuge or last-resort defense.  Also called a citadel or cavalier.

Lesser or Minor Fieldworks - earthworks constructed with an interior or rear-ditch.  Because soldiers stood in the ditch to fire over the parapet, the total relief rarely exceeded five feet.

Line of Battle - a tactical, linear formation of troops in which the front ranks stood nearly shoulder to shoulder and the rear ranks stood behind them in the intervals.  Eighteenth- and nineteenth-century armies deployed in such dense lines in order to concentrate their musketry in a single direction.  Since effective fire could be delivered only to the front, the entire line of battle needed to shift position to change the direction of fire.  Military earthworks reflected these linear tactics.

Lines at Intervals -- a line of mutually supporting detached works, typically redans, lunettes, or redoubts that were not connected by infantry parapets, also called a discontinuous line.  In theory, lines at intervals allowed defenders greater mobility to conduct an active defense.

Listening Well - a shaft sunk during siege operations to detect an enemy's attempt to tunnel under an entrenched position.  See Mine.

Loop-hole - a narrow slit through which a weapon could fire.

Lunette (Fr.) - a detached earthwork, open to the rear, composed of two faces forming a salient angle and two flanks, flanks and faces being of nearly equal length.  Called a bastion when connected to another lunette by a curtain wall.  Imprecisely applied to a demilune or epaulement.

Magazine - a secure, water-tight place to store ordnance supplies; in prepared works or fieldworks, a log or plank room or bunker covered over with a thick layer of earth to protect ammunition from accidental discharge or incoming artillery fire.  Most artillery fortifications occupied for any length of time had at least one magazine, depending on the number and types of guns.  A surviving magazine typically appears as a large mound of earth, sometimes with a depression in the top where underlying timbers have collapsed or in the side where the entrance used to be.  The entrance was to the rear, opposite any incoming fire.  Communication trenches or at least unobstructed paths for runners lead from the entrance to the gun platforms.  From visible remains, it is difficult to tell if a mound was a magazine or a bombproof.  A single mound within an artillery fortification is likely to have been a magazine, because engineers generally protected ordnance before men.

Maham Tower - platform of logs, earth, and gabions constructed during siege operations to allow besiegers to fire over the defenders' parapets.

Main Line of Defense - line along which the principal strength and effort of the defenders was concentrated.

Merlon - section of parapet between two embrasures.

Military Crest - shoulder of a hill or ridge rather than its actual crest.  The military crest is the highest contour of elevation from which the base of its slope can be seen without defilade.  When surveying an area for surviving earthworks, it is often useful to search along the military crest.

Mine - tunnel dug beneath an enemy fortification, either to undermine its foundations or to set off an explosion.  Mine tunnels are occasionally discovered today in association with siegeworks, usually when a portion of it collapses.  The best defense against enemy mining was counter-mining, digging tunnels to intercept the enemy's mine.

Moat - ditch in front of an earthwork that was purposely filled with water.

Mutual Support - two artillery or infantry strong points, each within the other's range and field of fire and able to assist the other if attacked.  Engineers typically designed a fortification so that its parts were mutually supporting.

No Man's Land - See Zone of Contention.

Oblique Fire - incoming fire that strikes the parapet or line of battle at an acute angle from left or right.  Incoming fire could be direct, enfilading, oblique, plunging, reversed, or ricochet.

Palisade (Fr.) - a phalanx of sharpened logs or fraise, anchored in a shallow ditch and slanted to the front as an obstacle to advancing infantry.  Also a wall of logs or stockade.

Pan Coupé (Fr.) -- a short straight stretch of parapet constructed across the capital of a salient angle, having the effect of reducing the angle's sector without fire.

Parade or Parade Ground - flat assembly area within a larger permanent or semi-permanent fortification; often adjacent to barracks or other garrison buildings; sometimes improved by leveling and draining.

Parallel - a parapet thrown up to confront defenses when conducting a siege by regular approaches.  The First Parallel was constructed out of range of the enemy's guns.  Saps were pushed forward fifty or a hundred yards to construct a Second Parallel, and so on, until reaching the ditch of the enemy fortification. Imprecisely applied to describe a curtain wall.

Parallel Fire - fire directed across the front of an entrenched line or line of battle.

Parapet  (It. parapetto, shield the chest) - a linear mound of earth built to defend against incoming fire.  The thickness of a parapet was determined by the armament that it was expected to withstand-for musketry, 5-7 feet; field artillery, 8-16 feet; for siege or naval guns, up to 35 feet.  The parapet consisted of an interior slope, usually revetted with logs, planks, rails, stones, sandbags, or fascines, so as to be nearly vertical, the superior slope or crest, which inclined slightly downward toward the enemy, and the exterior slope or outer face, which took the brunt of enemy fire.  The exterior slope typically inclined 45 degrees, the natural angle of repose for most soils.

Passive Defense - strategy of holding an entrenched position and awaiting the enemy's attack.

Peneplein (Fr.) - flat interior of an enclosed earthwork, synonymous in usage with terreplein.

Permanent Fortifications - defenses constructed to defend towns, garrisons, depots or other fixed positions that were intended to last for a long time with minimal repair.  A fort's ramparts could be constructed entirely of stone and brick or, if built largely of earth, would have masonry revetments within and without to deter erosion.

Picket - a guard or vidette.

Picket Holes or Skirmish Pits - See Holes and Pits.

Picket Line - a row of guards, or videttes, spread out in intervals and formed in advance of the main line to provide warning of an attack; a row of individual foxholes entrenched by the pickets.  Picket lines were advanced anywhere from 50-300 yards in front of the main lines, depending on the terrain and proximity of the enemy.

Platform - See Gun Platform.

Plunging Fire - fire directed from higher to lower ground.

Postern - See Sally Port.

Prepared or Provisional Entrenchments - See Deliberate Entrenchments. 

Priest Cap - a detached earthwork consisting of two faces joined in a reentrant and two long flanks extending toward the rear and inclining away from the open gorge.  The design served to converge the fire of the two faces on a specific target to the front.  The severity of the re-entering angle determined the distance to the point of convergence.

Profile - cross-section of an earthwork.  The higher and wider the parapet, the wider and deeper the ditch, the "stronger" the profile.  A simple rear-ditched rifle trench had a "weak" profile.

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