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Military Earthworks Terms

a glossary compiled by the National Park Service (2001)

Military Earthworks Terms

a glossary compiled by the National Park Service (2001)

Reference Notes

    Abattis or Abatis (Fr.) -- felled trees, arranged in the form of a hedge with trunks aligned and anchored in a shallow ditch. Branches were sharpened and interlaced pointing toward the enemy. Its purpose was to prevent surprise and to delay an attacking force within range of defensive weapons. Sometimes called a slashing.

    Active Defense -- strategy of defending a line by maneuver and counterattack.

    Advanced Works -- fortifications in advance of but still within firing range of the main works.

    Angle -- where two faces of a fortification meet. See Salient and Reentering Angles.

    Apex -- foremost salient angle of a fortification, that which protrudes farthest toward the enemy.

    Approach -- a trench dug to get closer to the enemy line, called a sap in siege operations.

    Artillery Strong Point -- a battery, redoubt, or bastion that served to anchor a larger system of fortifications.

    Artillery Works -- earthworks designed to protect artillery and to provide an effective field of fire.

    Back-ditch or Interior Ditch -- ditch dug behind a parapet. See Ditch.

    Banquette (Fr.) or Firing Step -- a shelf dug behind a parapet that allowed a defender to step up from the ground to fire over the parapet, then step back down under cover to reload. A banquette was only necessary when the parapet was higher than a man's armpits. It was a common feature associated with prepared fortifications, curtains, and detached works, such as redoubts. If a banquette survives, it is often blurred by soil eroding from the parapet.

    Balk -- a narrow barrier of earth within the ditch of an earthwork that was purposely left unexcavated. Balks sometimes marked divisions between units in the line. A balk might also serve as the base for a traverse made of logs.

    Barbette (Fr.) -- artillery positioned to fire over the parapet rather than through an opening in it. See Embrasure. A cannon firing en barbette had an unrestricted (180-degree) field of fire, but its gunners were more exposed to fire than one firing en embrasure. A barbette gun was raised to fire over the parapet by means of a large carriage or by a gun platform built up to the appropriate height. See Gun Platform.

    Bastion (Fr.) -- an angular work that projected outward from the main faces of a fortification. Its purpose was to eliminate defilade by directing fire along the front of an adjacent curtain wall. Like a lunette, a bastion consisted of four parts: two faces forming a salient angle oriented towards the enemy, and two reentering flanks that directed fire sideways across the faces of adjacent bastions. A curtain (or curtain wall) connected two or more bastions. See Lunette.

    Bastion Line -- a series of bastions joined by short curtains.

    Bastioned Fort -- an enclosed earthwork with bastions in the angles to provide fire along the fronts of the connecting curtains.

    Battery -- an artillery unit or a fortification designed to defend an artillery unit.

    Berm or Berme (Fr.) -- narrow ledge or shelf left at grade to separate the scarp of the ditch and the exterior slope of the parapet. When constructing high-relief defenses, workers stood on the berm to relay earth from the ditch up onto the parapet. The berm was sometimes left to retard slumping of the parapet, but many engineers felt that it assisted attackers in scaling the parapet and had it pared down after construction. Soil eroding from the parapet will typically blur a berm's outline.

    Blockhouse -- building constructed of heavy logs in the shape of a square, rectangle, or cross, to serve as a strong point for infantry or artillery. A ditch was often excavated around the exterior with the spoil thrown up against the wooden structure as a protection against fire and gunfire. Often part of the first floor of a blockhouse was below ground, while the upper floor, pierced with loopholes and embrasures, was built with an overhang so that defenders could fire down around the base of the structure. Blockhouses were used to defend railroad trestles, bridges, and depots, or served as a "keep" or place of final refuge in a larger fortress or stockade. The excavations associated with many blockhouses survive, although timbers were often scavenged for other uses. Some had brick or stone flooring and fireplaces.

    Bombproof -- a log or plank room or bunker covered over with earth to protect troops from artillery fire. A surviving bombproof appears as a large mound of earth, sometimes with an elongated depression in the top where underlying timbers have collapsed or in the side where the entrance used to be. See Magazine.

    Bottom of the Ditch -- flat space at the base of the ditch that separated the scarp and counterscarp.

    Boyau (Fr.) -- a communication trench, a sap pushed forward toward the enemy. Typically constructed in a zigzag pattern to prevent exposure to direct fire from the front.

    Breaching Battery -- a battery constructed during siege operations to enfilade a portion of the enemy's defenses or to batter down the enemy's walls or parapets.

    Breastwork -- a linear earthwork that was tall enough to cover the chest of a man standing behind it. A breastwork could also be constructed of ad hoc materials, such as logs, stones, barrels, or cotton bales. The term is used very generically.

    Bulwark -- See Rampart.

    Capital -- the imaginary line that bisects an earthwork's salient angle.

    Casemate -- enclosed and roofed-over artillery position. The gun fired through an opening called an embrasure. Casemates vaulted with stone were a basic component of permanent masonry fortifications. Casemates were constructed only rarely in the field with logs and earth.

    Cavalier -- See Keep.

    Cheek -- side of an embrasure, often reinforced by gabions or sandbags.

    Caponière (Fr.) -- projection from the front of a curtain wall that enabled infantry or artillery to fire into an exterior ditch.

    Cheeks -- sides of an embrasure, often reinforced with gabions, sandbags, or logs.

    Chemise -- a revetment for an earth embankment.

    Chevaux-de-frises (Fr.) -- portable obstacles built of logs with projecting sharpened stakes, joined together by chains; called "horses of Friesland" where the device was invented in the mid-1600s.

    Circumvallation -- siege lines built to "invest," or enclose, the enemy's defenses. See Countervallation.

    Citadel -- See Keep.

    Column of Fire -- a volume of fire directed perpendicular to the parapet. Entrenched soldiers tended to fire directly to their front when under attack, rather than side to side. To deliver fire where it was most needed, engineers changed the orientation and relationships of a fortification's faces and flanks. Each segment of parapet had a specific column of fire that swept the front or interlocked with fire from an adjacent segment.

    Command -- height of an earthwork above grade.

    Communication Trench -- a ditch and parapet that connected one part of an entrenchment with another to move troops and supplies. These were sometimes simple shelter trenches, serving as arteries to direct reserves to some portion of the line. Called a covered way if deep enough to conceal movement.

    Continuous Line -- a line of fortifications presenting a solid front to the enemy. Parapets, or Curtains, connected all of the artillery strong points on the line. See Lines at Intervals.

    Corbeil or Corbeille (Fr.) -- a form of gabion; a small wicker hamper wider at the top, placed in a row along the parapet and filled with earth. The tapered shape left a musketry loop-hole between corbeils.

    Corduroy Road -- logs laid side-by-side in a roadbed to make it passable in wet weather. The same technique was often applied to gun platforms to support artillery pieces.

    Counterbattery Fire -- artillery fire directed at the enemy's artillery in an attempt to silence or disable the guns. Because of the threat of counterbattery fire, artillery positions were typically built stronger and more massive than adjacent infantry entrenchments.

    Countermining -- See Mine.

    Counterscarp -- outer or exterior slope of a ditch. See Scarp.

    Countervallation -- siege lines built in conjunction with lines of circumvallation to protect the rear of the besieging force from assault by a relief force or from raids.

    Covered or Covert Way -- in permanent fortifications, a walkway extending around the outside of the moat or ditch of the main line; in fieldworks, a ditch and parapet designed to protect and conceal the movement of troops and supplies to the front lines from camps or supply caches in the rear. A covered way was not "covered," in the sense of being roofed over; it provided cover from gunfire.

    Cremaillière (Fr.) or Indented Line -- a stepped or saw-toothed line of fortifications, designed to generate crossing fires all across the front of the line.

    Crest -- See Superior Slope.

    Crossing or Interlocking Fire -- fire that converged on the same target from two different points. When laying out a line of defense, engineers sought to generate interlocking fire whenever possible. See Column of Fire.

    Crownwork -- a detached earthwork open at the gorge, formed of a central bastion and two flanking demilunes with two long flanks extending to the rear and inclining toward the gorge.

    Cunette (Fr.) -- a narrow drainage ditch running along the bottom of a trench. Drainage was a continual concern whenever an earthwork was occupied for any length of time. Drainage ditches have been observed to survive, typically within semi-permanent forts, siegeworks, and larger batteries.

    Curtain or Curtain Wall -- a straight line of parapet that connected two bastions or artillery strong points, technically with an exterior ditch.

    Dam -- often used in conjunction with military earthworks to flood an area for defensive purposes.

    Déblai -- the earth removed from an excavation that provided the bulk of the material used to construct a rampart or parapet. See Spoil.

    Dead Angle -- See Sector without Fire.

    Defilade or Dead Ground -- a ravine, gully, or depression within range of an earthwork's weapons that could not be seen or fired into from the defenders' position.

    Deliberate Entrenchments -- defenses constructed in anticipation of need, to defend a town, depot, or bridge, for example, typically constructed with a front or exterior ditch. If defending an important position and occupied for a long period of time, deliberate earthworks might be improved to a semi-permanent condition. Magazines and bombproofs were built. The parapets might be sodded with grass, revetments faced with sawn planks or stone, roads and ramps paved with flagstones, a well dug, and a more complete drainage system installed. Frame barracks and storehouses might be constructed within or adjacent to the earthworks for the garrison.

    Deliberate Fieldworks -- improvements made to an existing line of rapid entrenchments, typically the addition of detached works for artillery. Also siegeworks.

    Demi-bastion (Fr.) -- an angular work that projected outward from the corner of an enclosed or detached earthwork. A demi-bastion consisted of one face and one flank forming a salient angle. The flank directed fire across the front of an adjacent face or curtain.

    Demilune (Fr.) -- a crescent shaped parapet protecting a single cannon, typically ditched in front. Also called an epaulement; in permanent fortifications, a component of the bastion. The term was often used interchangeably with lunette, but this is imprecise.

    Dentate -- zigzag or saw-toothed parapet designed to direct fire obliquely left and right across the front, designed to create interlocking fields of fire. See Cremaillière Line.

    Detached Works -- fortifications constructed in advance of the main line to delay an enemy's approach or built as components of a line of intervals, generally redans, ravelins, lunettes, or redoubts. Other variations included swallow's tails, hornworks, crownworks, and priest caps.

    Direct Fire -- incoming fire striking perpendicular to the parapet or line of battle. Incoming fire could be direct, enfilading, plunging, reversed, and ricochet.

    Discontinuous Line -- See Line of Intervals.

    Ditch -- excavation providing soil to construct a parapet. A ditch could be in front of the parapet (front-ditch or exterior), behind it (back-ditch or interior), or on both sides (double-ditch). Engineers preferred front-ditch construction whenever time and labor permitted, as it created a stronger profile. Batteries, redans, lunettes, and redoubts were consistently constructed with a front-ditch. Back-ditch construction was the fastest way to entrench, and therefore was used most often for rapid infantry entrenchments. A double-ditch resulted from digging in front to widen an existing back-ditch parapet, from constructing a covered way behind a front-ditched line, or from capture and refacing. Some evidence of the ditch-a shallow trough-often survives even if its parapet has eroded away. The scarp and counterscarp are the inner and outer slopes of the ditch.

    Double-ditch -- parapet with both an interior and exterior ditch. Double-ditching was used to widen an existing back-ditch parapet or to provide a covered way behind a front-ditch parapet. An earthwork that was captured and turned (refaced) would have a double ditch. See Ditch.

    Drainage Ditch -- See Cunette.

    Dugouts and Bunkers -- rectangular excavations, usually 5-10 feet on a side, associated with the principal defenses of an earthworks complex. These typically served a command or logistical function. On rare occasions in the field or during siege operations, dugouts might be roofed or partially roofed with logs and earth.

    Earthworks -- any earthen structure excavated for military purposes. In simplest form, a defensive earthwork was composed of a parapet or mound of earth and a ditch from which the earth was excavated.

    Earthworks Complex -- consists of the Main Line of Defense, a Zone of Occupation behind the main line, a Zone of Fire in front of it, and a Zone of Contention (No Man's Land) separating advanced positions of the combatants. The entire fortified front, taking in both combatants, might be a mile ore more deep with each zone identified by a specific grouping of features and artifacts.

    Embrasure (Fr.) -- a wedge-shaped opening cut to allow artillery to fire through the parapet. A cannon firing en embrasure had a restricted (45-degree) field of fire but the parapet protected the gunners. The sides, or cheeks, of an embrasure often were reinforced by logs, planks, stones, sandbags, or gabions. Embrasures were common features of artillery fortifications and often survive as an indentation in the otherwise uniform parapet crest. Not all indentations are embrasures. Typically, there is other evidence of the presence of artillery-a gun platform and gun ramp, for example. A single gun might have had multiple embrasures. See Barbette.

    Enceinte (Fr.) -- "body of the place," area of a fort or redoubt enclosed by the parapet.

    Enclosed Work -- an earthwork designed to be defended from all sides. See Redoubt.

    Enfilade or Enfilading Fire -- fire from the flank that swept along the length of a parapet or line of battle. Enfilading fire could be particularly destructive as incoming rounds might strike multiple targets and no return fire could be brought to bear. Traverses were often constructed behind a parapet to limit casualties caused by enfilade. Incoming fire could be direct, enfilading, oblique, plunging, reversed, or ricochet.

    Entanglement -- obstacles placed in front of an earthwork to trip up and delay attackers, sometimes used to refer to an abattis. During the Civil War, telegraph wire was strung from stump to stump at shin level to form a "wire entanglement." Most wire was retrieved or scavenged during or after the war, so little would be expected to survive archaeologically.

    Entrenchment or Intrenchment -- generic term for any form of earthen fortification. In common usage, terms like breastwork, trench, entrenchment (intrenchment), curtain, and fieldworks were applied with little precision.

    Epaulement (Fr.) -- See Demilune.

    Escarp, Escarpment (Fr.), or Scarp -- rear or inner slope of a ditch. In a front-ditch earthwork, a continuation below grade of the exterior slope of the parapet. See Counterscarp.

    Exterior Ditch -- See Front-ditch.

    Exterior Slope -- outer side of the parapet that faced the enemy and intercepted incoming fire. The exterior slope typically inclined 45 degrees, the natural angle of repose for most soils. The interior slope was more vertical to enable defenders to stand directly behind it. Nearly all extant earthworks in original condition will display some difference in angle between the exterior and interior slopes. See Interior and Superior Slope.

    Face -- a straight segment of parapet making up a larger earthwork that delivered direct or oblique fire to the front.

    Facing -- covering or treatment of a slope with sod, sandbags, stone, or other materials. See Revetment.

    Fascine -- tightly bound bundle of saplings used to reinforce a parapet or in revetment. Evidence of the use of fascines might appear as a darker stratum of soil in an excavated cross-section. See Revetment.

    Field of Fire -- area within weapons range that can be seen and swept by fire. Fields of fire were often improved by slashing (cutting down) all of the trees or pulling down buildings in front of the line.

    Fieldworks -- earthworks constructed by armies while actively campaigning, whether on the battlefield or in camp. Often hasty or rapid entrenchments.

    Fill -- logs, rails, stones, or other available materials used to add bulk to the parapet; typically gathered and placed along the intended line before digging begins.

    Fire -- organized and directed discharge of weapons.

    Fire Pits or Mess Holes -- See Holes and Pits.

    Flank -- left or right end of a line of battle or position; side; a segment of parapet thrown back to protect the side of a position or to allow defenders to deliver fire across the front of an adjacent face.

    Flanking Fire -- fire directed from one segment of parapet to sweep the front of an adjacent segment.

    Flêche (Fr.) -- a small redan with a central, bisecting traverse giving it the appearance of an arrow.

    Fort -- an enclosed fortification defended by artillery; a complex, multi-component earthwork; a wooden stockade with corner blockhouses, often with ditching or other earthen components; generically, a military base.

    Fortification -- earthen works or other structures erected to defend a place or position.

    Fortress -- a system of defenses designed to work together as a whole to defend a fixed position. Often a permanent fortification.

    Fossé (Fr.) -- an exterior ditch fronting a rampart or curtain.

    Foxhole -- an individual shelter hole. See Holes and Pits.

    Fraise (Fr.) -- row of pointed logs set close together and inclined toward the enemy, often erected in the exterior ditch of a redoubt to prevent attackers from scaling the parapets. Sometimes called a palisade.

    Front -- exterior, toward the enemy.

    Fronting -- orientation of an earthwork vis-à-vis the enemy.

    Front-ditch or Exterior Ditch -- ditch on the outside of a parapet designed as an additional obstacle to assault. A front-ditch allowed the parapet to have greater bulk and a stronger profile than rear-ditch construction. This was the engineers' preferred method and was consistently applied to prepared fortifications, to detached works, and artillery fieldworks. It is common to find a mix of front-, rear-, and double-ditch entrenchments in a single continuous line. See Ditch.

    Fully Stocked Forest Stand -- This refers to a full overstory canopy capable of replenishing the forest floor. Foresters typically use basal area to measure stocking in a forest. A rule of thumb is that the lower limit of full stocking is around 60 square feet of basal area per acre. In pine and pine-hardwood forests, it is 80 square feet per acre. Basal area (BA) = 0. 005454d 2 BA is basal area in square feet and d = tree diameter in inches. Summing the basal area from all trees over an acre provides basal area per acre which is a measure of stocking. Basal area for mature deciduous forests in the eastern United States generally range from 100 to 150 square feet per acre.

    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.

    Ramp -- an incline leading up to the banquette or allowing access to a gun platform.

    Rampart -- a broad embankment of earth that supported the functioning elements of a permanent or semi-permanent fortification. The parapet and banquette were built at the front of the rampart; ramps moved troops from the interior of the work onto the terreplein of the rampart. In early forts, a rampart was often improvised by constructing double parallel revetments of logs and filling the intervening space with stones and hard-packed earth. Ramparts typically were not a component of field fortifications but appeared occasionally in simpler form in some artillery works. Sometimes called a bulwark.

    Rapid Entrenchments -- fieldworks constructed in the presence of the enemy, usually with a rear or interior ditch and often with ad hoc materials for fill and revetment, also called hasty or temporary entrenchments. Although built "hastily, " these were rarely built "carelessly," as the modern use of the word might imply. Experienced soldiers could throw up a shelter trench sufficient to absorb small arms fire in less than an hour with only rudimentary tools.

    Ravelin -- a detached earthwork open to the rear with two long faces forming a salient angle and two short flanks. See Detached Works.

    Rear -- interior, away from the enemy.

    Rear-ditch or Interior Ditch -- ditch in which soldiers stood to fire over the parapet; most commonly used in rapid infantry entrenchments. Rear-ditch was the fastest way to entrench because each shovel of earth lowered the ditch and at the same time raised the parapet. See Ditch.

    Redan (Fr.) -- a detached fortification with two faces forming a salient angle, often built as an outer work to cover an advanced position. The work was open at the rear. A redan was a common form of all military eras. When bisected by a traverse down its center (along the capital line), it was called a flêche, or "arrow." When connected to adjacent strong points by curtain walls, it served as a caponière.

    Redan Line -- a series of redans connected by curtains.

    Redoubt -- an enclosed fortification designed to be defended from all sides. The trace of a redoubt could be square, polygonal, or occasionally circular. A redoubt could stand alone as a detached work, serve as a place of refuge within a larger fortification, or be incorporated into a continuous line of entrenchments as an artillery or infantry strong point. Redoubts were a common feature of all military eras.

    Reentering Angle or Reentrant -- angle in an earthwork or line of earthworks that points toward the rear and away from the enemy. Systems of earthworks were purposely designed with both reentering and salient angles.

    Reface -- to "turn" or change the facing of an earthwork.

    Relief -- distance from the crest of the parapet to the bottom of the ditch; relief is a component of the profile.

    Regular Approaches -- siege operations conducted by building saps, parallels, and breaching batteries, based largely on a system devised for the French armies by Sebastien le Prestre de Vauban (1633-1707).

    Regular and Irregular Works -- enclosed earthworks. Regular works were based on classic models-square or six-sided redoubts, and bastioned forts-and generally appeared balanced in proportion and symmetrical in trace. Irregular works were adapted to the peculiarities of the terrain and took a variety of shapes and traces. Although less "elegant" in terms of geometry, irregular works were often measurably stronger than the more rigid, classical prototypes.

    Remblai -- the material used to construct a rampart or parapet, the bulk of this material provided from earth removed by excavation. See Spoil.

    Retrenchment -- a secondary line of earthworks built to seal off a gap in the main line or to prevent a breakthrough.

    Reversed Fire -- incoming fire that strikes the rear of a parapet or line of battle. Incoming fire could be direct, enfilading, oblique, plunging, reversed, and ricochet.

    Revetment -- retaining wall constructed to support the interior slope of a parapet. Made of logs, wood planks, fence rails, fascines, gabions, hurdles, sods, or stones, the revetment provided additional protection from enemy fire, and, most importantly, kept the interior slope nearly vertical. Stone revetments commonly survive. A few log revetments have been preserved due to high resin pine or cypress and porous sandy soils. After an entrenchment was abandoned, many log or rail revetments were scavenged for other uses, causing the interior slope to slump more quickly. An interior slope will appear more vertical if the parapet eroded with the revetment still in place.

    Ricochet Fire -- fire that strikes the ground first then bounds into the air, used primarily by artillery firing a round, solid shot. The glacis was shaped to deflect ricochet rounds up and over the parapet rather than into it.

    Rifle Pits -- generically, any grouping of light, rapid entrenchments, usually discontinuous, with a rear-ditch and low parapet. See Holes and Pits.

    Rifle Trench -- a parapet for infantry, typically thrown up rapidly with a rear-ditch. Also called a shelter trench.

    Salient -- a portion of a system of earthworks that protruded or bulged outward toward the enemy.

    Salient Angle -- an angle in a work or line of earthworks that pointed toward the enemy. See Reentering Angle. Systems of earthworks were designed purposely with both reentering and salient angles.

    Sally Port -- opening left in the parapet as an entrance to an enclosed earthwork. All enclosed earthworks had a sally port; called a postern when vaulted or roofed to form a tunnel.

    Sandbags -- used to strengthen prepared entrenchments and siegeworks, often filled off-site and transported to the work under construction. A stratum of sand overlying a different base soil, particularly in an artillery work, might indicate the use of sandbags.

    Sap -- a trench built to connect one parallel to the next in order to advance siegeworks, sometimes built as a zigzag approach or straight with internal traverses. See Regular Approaches.

    Sap Roller -- a large wickerwork cylinder rolled ahead of a crew to absorb incoming fire as it worked on a sap.

    Sapper -- a pioneer or engineer engaged in digging field or siegeworks.

    Scarp, Escarp, or Escarpment -- inner slope of the ditch, as opposed to counterscarp, the outer slope of a ditch. Both scarp and counterscarp are below grade and are visible components of all ditches.

    Sector Without Fire -- area in front of a salient angle into which the defenders cannot fire. A sector without fire was extremely vulnerable unless defended by fire directed from another part of the fortification.

    Shelter Trench -- a simple rifle trench for infantry, typically with a rear-ditch.

    Siege Operations -- systematic entrenching to approach an enemy's defenses, using classic engineering techniques. See Regular Approaches.

    Siegeworks -- earthworks built to advance or retard siege operations.

    Skirmish Line -- soldiers deployed at intervals in front of the main line of battle to harass the enemy and delay any enemy advance; a row of individual foxholes entrenched by the skirmishers. Skirmish lines were advanced anywhere from 50-300 yards in front of the main lines, depending on the terrain and proximity of the enemy. Sharpshooters often manned the skirmish line.

    Skirmish Pits or Picket Holes -- See Holes and Pits.

    Slashing -- cutting down all trees in front of a line to create a clear field of fire. Trees were felled in the same direction with branches toward the enemy, serving as an obstacle to attack. Downed trees might then be trimmed and arranged more formally into an abattis.

    Slit Trench -- slang for a short trench, similar to a rifle pit, constructed for 3-5 men. Often found in a picket line interspersed with foxholes or as shelter in the rear of a main line.

    Spoil -- earth removed from an excavation, termed in French the déblai. The spoil provided the bulk of the remblai, that is, the material used to construct a rampart or parapet.

    Star Fort -- an enclosed work with alternating salient and reentering angles. A star fort might have from four to eight salient angles projecting toward the enemy. This was a popular form until the middle of the Civil War, but many engineers considered it to require more work than needed for a strong defense. Examples of star forts survive from various time periods.

    Stockade -- generically, a log fort; when used as an adjunct to earthworks, a vertical wall of logs tied or nailed together to protect the flank or gorge of a battery, lunette, or redoubt. Loopholes were cut in the logs to allow for rifle fire. The exterior of the stockade wall might be ditched with the earth thrown up against the logs. Archeological excavation might reveal evidence of the postholes or remains of the post in the ground.

    Strong Point -- a dominating position, usually high ground, defended by entrenched artillery or a concentration of infantrymen; an artillery work within a continuous line of entrenchments.

    Superior Slope -- crest of the parapet on which soldiers rested their weapons to fire. The interior slope was nearly vertical so that a man could stand comfortably against it. The superior slope inclined slightly toward the enemy. The exterior slope, which intercepted most incoming fire, inclined more abruptly. See Parapet.

    Supply Cache -- a rectangular excavation, usually 5-10 feet on a side and three feet deep, found in rear of the Main Line of Defense. See Earthworks Complex. These served as temporary storage for boxes of food or ammunition and are found in sheltered terrain adjacent to a road or a covered way. On rare occasions in the field or during siege operations, a supply cached might be roofed or partially roofed with logs and earth.

    Swallow's Tail -- a detached earthwork consisting of two faces joined in a reentrant and two long flanks extending toward the rear and inclining toward the open gorge.

    Tenaille (Fr.) Line -- a series of adjacent redans, of equal or differing sizes, joined at the flanks with no connecting curtains.

    Terreplein (Fr.) -- ground level, grade; generically a level area inside an enclosed fortification; in permanent fortifications, the flat surface of the rampart behind the parapet.

    Tête-de-pont (Fr.) -- an entrenched bridgehead with both flanks anchored on a river, designed to hold a river crossing.

    Throw Up Works -- to entrench. Earthworks were described as being "thrown up."

    Trace -- outline of a fortification as drawn on a plan or "traced" upon the ground. In terms of engineering, the trace of an earthwork was its most important characteristic. To be effective, the trace should take advantage of the military strengths of the terrain and mitigate its weaknesses; its design should accomplish its purpose in the overall plan of defense; its length should be adjusted to the number of soldiers designated to hold the position.

    Traverse -- a short segment of parapet used to prevent incoming enfilade fire from sweeping the length of a line, to protect the rear wall of an enclosed work from a plunging fire from the front, to cover a sally port, or to provide extra protection for a magazine or supply cache. Traverses were sometimes built of or reinforced by gabions and were usually constructed perpendicular to incoming fire, rather than perpendicular to the defensive parapet. In rapid entrenchments, traverses might be constructed entirely of logs.

    Trench -- usually short for entrenchment, sometimes referring to the ditch of an entrenchment or to an auxiliary entrenchment in rear of a rampart.

    Trous de loup (Fr.) -- rows of pitfalls, 4-6 feet deep, dug in checkerboard fashion in front of an earthwork to obstruct to an attacking force. Each cone-shaped pitfall concealed a sharpened stake.

    Turned Works -- an entrenchment captured by the enemy and refaced, resulting in ditching on both sides of the parapet.

    Work -- any discrete component of a system of fortifications, applied most often to detached defenses, to forts, or artillery strong points.

    Zigzag Trench -- See Boyau.

    Zone of Contention -- No Man's Land, the area separating the deployed skirmishers of the combatants, often defined by the foxholes of the opposing skirmish lines. Because skirmishers tended to advance or withdraw according to nuances of the terrain and localized pressure, the width of this zone fluctuated. See Earthworks Complex.

    Zone of Fire or Kill Zone -- area between the Main Line of Defense and the advanced skirmish or picket line, typically no wider than the effective ranges of standard infantry weapons. In this zone, soldiers cut down trees to clear a field of fire and often erected obstacles, such as an abattis or entanglements, to slow down and break up an attack. Nothing would remain from such obstructions unless it was the shallow ditch that anchored the abattis. One might find larger dugouts that held reserve pickets that could be fed out to the skirmish line as needed. See Earthworks Complex.

    Zone of Occupation -- area behind the Main Line of Defense. This zone might extend 200 yards or more behind the front, depending on the terrain. In this zone were activities of logistics and support, which sometimes left evidence in the form of support trenches, dug-out supply caches, bunkers for officers and non-combatants, or covered ways through which troops and supplies could move unseen from the rear to the front line. In some cases, artillery positions were constructed to fire over the front lines at distant targets. See Earthworks Complex.