Sally port, parapet wall and ditch visible at Fort Stedman , Petersburg National Battlefield, photoby Jon Buono.
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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
Grade - original ground level. Ditch is below grade; parapet
is above grade.
Greater or Major Fieldworks - earthworks constructed with an exterior
Gun Pit - an entrenched artillery position, a platform, demilune
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
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
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
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'
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
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
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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