Glossary
Military Earthworks Terms

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.

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.

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