Johnson’s defense

Siege and engineer glossary

The vocabulary an engineer’s account of a siege is written in.

Johnson was an engineer writing for officers, and he does not stop to explain himself. These are the terms a reader has to have to follow him through a fort that was being taken apart and rebuilt at the same time. The examples are from his own pages.

Barbette: Mounted on the ramparts to fire over the parapet rather than through an embrasure. Barbette guns had the command and the arc; they also stood in the open, and at Fort Sumter they were the first to go.
Berme: The narrow level ledge between the foot of a wall and the water or ditch below it. Fort Sumter's was ten feet wide on the gorge and narrower elsewhere, and it is where Mathewes laid his cushion of sandbags to catch a sixteen-thousand-pound gun dropped forty feet from the parapet.
Blindage: A screen of timber and earth built to stop splinters and fragments. The splinter-proof blindage at the base of the gorge was one of the few safe places left in the fort by September 1863.
Bombproof: A chamber roofed heavily enough to stop a descending shell. Battery Wagner's — thirty by a hundred and thirty feet — held perhaps half its garrison, and Johnson is careful to say it did not hold them all.
Caponnière: A small covered work projecting from a fort to sweep the ditch or approach with fire. Fort Sumter's, near the sally-port, mounted two casemate howitzers to defend the quay and pier.
Casemate: A vaulted chamber in the body of a fort, with an embrasure for a gun. Fort Sumter had two tiers of them; by 1864 most were filled with sand, and the sand was the fort.
Chassis: The inclined frame on which a heavy gun's carriage runs back and forward. At Christmas 1863 the chassis of a 10-inch columbiad, run forward into battery, served the headquarters mess for a dinner table.
Columbiad: A heavy American smoothbore, chambered for shell as well as shot. The 10-inch columbiad was the heaviest gun the Confederacy could put in Charleston harbor, and it threw a 128-pound projectile.
Counterfort: A buttress built behind or against a wall to hold it. The stone counterforts on the exterior of Fort Sumter's gorge, raised a year before the bombardments to protect the lower magazines, came through untouched; the brick continuation above them, two months old, did not.
Embrasure: The opening in a wall or parapet through which a gun fires. Fort Sumter's upper-tier embrasures had been bricked up in 1861 to a narrow loophole; a shell went through one of those fillings on 7 April 1863 and set fire to the bedding behind it.
En barbette: See barbette.
Enfilade: Fire down the length of a line or face, so that a shot that misses one thing hits the next. Fort Sumter's traverses were built against it, and the Federal batteries on the marsh line of Morris Island were sited to obtain it.
Fraise: A row of pointed stakes set below the crest of a slope to stop men climbing it. At Fort Sumter the fraises came in sections on a light frame, were set on the practicable slopes every evening at dusk and taken in every morning before daylight, for seventeen months.
Gabion: An open cylinder of woven brush filled with earth — the standard unit of field fortification. Gabions held the slopes of Fort Sumter's sand in place in the last year, and were part of the nightly requisition from the city.
Gorge: The rear face of a work. Fort Sumter's gorge faced Morris Island, took most of the breaching fire, and was the one wall the defense could not let go: filling its seventeen rooms with wet cotton bales laid in sand is what Johnson says preserved the fort.
Grillage: A framework of heavy timbers laid to spread a load, or to hold ballast against a wall. Fort Sumter's was begun on the berme of the sea-front and never carried above five feet; the Marsh Battery's was what kept the Swamp Angel out of the mud.
Machicoulis gallery: A projecting gallery with openings in its floor, for firing straight down at anyone at the foot of the wall. One was cut in Fort Sumter's city front, and it is the opening the men trapped upstairs by the December fire were passed down through.
Merlon: The solid mass of parapet between two embrasures. Merlons and traverses were raised on Fort Sumter's sea face with sand carried up the spiral stairs in bags, thirty-five feet above the parade.
Parade: The open interior of a fort. Fort Sumter's was mined four feet deep for sand to fill the casemates, went below the level of high water, collected stagnant water, and had to be drained by a well and a pump.
Parados: A mass raised behind a position to stop fire coming from the rear. The great sand parados over the three-gun battery is what let three heavy guns live in a fort the enemy could fire into from behind.
Parallel: A trench dug across the front of a besieged work, parallel to it, from which the next approach is pushed. Gillmore's first parallel before Battery Wagner was 1,350 yards out, the second 870, the third 540.
Reverse fire: Fire that strikes a work from behind. It is the tactical fact of this book: from Morris Island the Federal guns took Fort Sumter's northern casemates in reverse, cut the piers out from under the arches, and brought the ramparts down from the inside.
Sally-port: The gate of a fort. Fort Sumter's original one on the gorge was closed and buried under sandbags in July 1863, and a new one was cut through a lower casemate on the city front, with a timber wharf built out from it into deep water.
Sap: A trench pushed forward toward a work under cover, by men working at its head. The sap before Battery Wagner met an ingenious system of torpedo mines, exploded by the tread of a man walking over them.
Scarp: The outer face of a fort's wall. Fort Sumter's scarp was five feet thick, unbonded to the casemate piers behind it — which, Johnson argues, is why it cracked the full forty feet of the western front under the shock of the guns.
Terreplein: The level surface on top of the ramparts, behind the parapet, where barbette guns stand. When a casemate arch was destroyed the terreplein above it went down with the gun, carriage and platform.
Traverse: A mass of earth or sandbags raised across a rampart to stop fire running along it. Fort Sumter's four on the sea face were thirteen feet high above the terreplein and fifteen feet thick at the top.
Water-battery: A battery close to the water, sited to fire on ships. Fort Johnson's was seven heavy guns bearing only on the harbor — and therefore useless, on 3 July 1864, against an attack that came in from behind it.