Fort Terminology - The Main Fort

jrweaver

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I thought I'd start off 2021 by picking up on the Fort Terminology thread, moving to the Main Fort. Everything inside the ditch is considered the main fort, and some structures that extend into the ditch are also part of the main fort. I'll use the same format I used in the outworks, and encourage comments and corrections!
Again, this is terminology as it is applied to the Third System of coastal forts. The terms generally apply to earthwork forts, but may have a few variations. As most of you know, the Third System forts are masonry with a mixture of earthen and masonry ramparts.
 

jrweaver

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The enceinte (pronounced on SENT) of the fort is the mass of the fort, defined by the overall shape. The shape is expressed by the geometric term based on the number of sides, and carries the modifier of "regular" or "irregular." A regular polygon has equal-length sides, where an irregular polygon does not. The enceinte of a fully symmetrical, five-sided fort would be expressed as a regular pentagon. Fort Jackson is a great example of a fort that has a regular pentagon with bastions as an enceinte.

25-1 Jackson Inside Scarp Color.jpg
 

jrweaver

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There are several terms that are used in describing the enceinte of a fort. A front of a fort is that area facing the enemy; on the drawing above that is from bastion salient to bastion salient. On a fort without bastions, that would be the straight area facing in any particular direction. The face of a fort is the front (there can be multiple faces) that provides the primary defense. That would be the front or fronts toward the water in a coastal-defense fort. The primary front (or fronts) would be the front where ships would be under the guns for the longest time; the secondary front (or fronts) would be the front where ships would be under the guns of the fort for a shorter time. Fort Jackson, above, had two primary riverine fronts and no secondary fronts.
The gorge of a fort is the face away from the face (or faces), and usually contains the sally port.
In a fort with bastions, the curtain is the portion of the fort wall between the bastions. In a fort without bastions, the curtain is the straight wall of the fort. Forts without bastions do not have salients; this would be considered a highly vulnerable portion of the fort as it can be fired on from multiple directions. Instead, a pan coupe is use to "cut off" the corner. This wall angles between the adjacent curtains. The drawing of Fort Sumter below shows the pan coupe and curtains of the fort.

Sumter Plan Drawing showing pan coupe and curtain.jpg
 

jrweaver

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The next topic is the bastion. This is a key element in the defense of a fort. Vauban is credited with popularizing, if not inventing, the bastion and its use in fort designs during the 17th Century and beyond. I recently saw a picture of a recently built defensive structure in Afghanistan that had bastions! They are still used.
The bastion has two primary functions. First, the salient, or outward angle, of a fort is considered a weak point because it can be fired upon from multiple directions. A bastion placed at the salient of a fort strengthens this point. In the Third System, especially the early part where Bernard was responsible for the designs, the salients of the bastions were earth-filled. This means that if the masonry wall is knocked down, what remains is a steep slope that still provides a strong defense.
The second function of a bastion is to provide flanking, or enfilading, fire down the curtain of the fort. A bastion is designed such that there is no area on the outside of the fort that is not under fire from the flanks of the bastion. The following sketch shows the fields of fire from two adjacent bastions. The two bastions provide a defense of the curtain as well as the faces of the bastions.
2-16 Bastions Fields of Fire Graphic..jpg

The parts of a bastion are shown in the following sketch. The flanks are generally casemated for flank howitzers, short-range cannon that fire primarily grapeshot and canister shot. Grapeshot is a stand of balls approximately the size of bocce balls that spread out on leaving the barrel. Canister shot is a coffee-can-like container with balls from musket-ball-size to golf-ball-size. The canister comes apart as it leaves the barrel spreading the balls in a similar manner to grapeshot. In both cases, the balls will ricochet off the outside wall of the fort as well as the counterscarp wall, causing a wild array of balls flying through the ditch.
In addition, bastion flanks sometimes contain loopholes in addition to howitzer embrasures. This allows musket/rifle fire in addition to the fire of the flank howitzers.
The key to a bastion is that this defense can be provided while the defenders are protected by the fort walls. The following picture shows the flank of a bastion at Fort Clinch on Amelia Island, Florida, at the mouth of the St. Mary's River. Note the howitzer embrasures and rifle loopholes.
11-39 Clinch Bastion Flank.jpg
 

jrweaver

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A structure that can be considered as part of the main fort or a part of the outworks is the caponier (pronounced cap on YEAR). If a caponier is attached to the main fort, it is generally considered part of the main fort. If a caponier is detached from the main fort, it is generally considered part of the outworks. Below is the caponier at Fort Hamilton, guarding The Narrows at New York Harbor. It is a detached caponier, designed only for defense.
9-23 Hamilton Caponier.jpg


There are two general types of caponier that are attached to the main work. All caponiers provide defensive capability, either with loopholes or embrasures or both. One type is single-ended, only providing defensive capability. The other type is a passageway as well as a defensive structure. The pictures below are the caponier at Fort Washington on the Potomac River, a single-ended caponier for defense only.
Washington Caponier.jpg

10-7 Washington Caponier Interior.jpg


The second type of caponier is a passageway caponier, such as the one at Fort Tompkins, guarding The Narrows of New York Harbor. It provides defense of the ditch as well as passage between the main fort and the counterscarp gallery.
9-33 Tompkins Caponier.jpg
 

Lubliner

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My question about the caponier at Fort Hamilton and Fort Washington above, both being of the outer works; without a passageway for safety upon being overrun or being bombarded out, how were these men protected and allowed to reenter the fort during an attack?
Thanks for the explanations above. It is a great help!
Lubliner.
 

jrweaver

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The outside wall of a fort is called the scarp. Almost all Third System forts have a masonry scarp, either brick or stone. The only exception is Fort Scammel in Portland, Maine, which has a masonry-revetted earthen scarp. The scarp runs from the foundation of the fort - often a log grillage or stone - to the top of the wall. At or near the top of the wall is an overhang that keeps water from running down the face of the masonry, like a modern-day eave trough. This overhang, usually stone but sometimes brick, is called the cordon.
The following picture shows the scarp with the cordon at Fort Morgan on Mobile Point, Alabama.
2-17 Morgan bastion 2.jpg

Atop the cordon is the exterior slope, generally earthen, designed to absorb the impact of artillery shot and shell. The exterior slope is relatively steep, and is joined by the superior slope which continues upward at a shallower angle. The superior slope may be earthen or masonry, depending on the fort. The highest point of the superior slope is the parapet. The parapet is formed by the breast-height wall.
1609558720977.png


The picture below shows the exterior slope, the superior slope, and the parapet at Fort Monroe, Hampton, Virginia. Erosion has softened the distinction between the slopes, but they can still be seen.
1609559077056.png
 

jrweaver

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My question about the caponier at Fort Hamilton and Fort Washington above, both being of the outer works; without a passageway for safety upon being overrun or being bombarded out, how were these men protected and allowed to reenter the fort during an attack?
Thanks for the explanations above. It is a great help!
Lubliner.
The caponier at Fort Washington was directly connected to the fort, entered from the ramparts. At Fort Hamilton, the caponier was across the inner portion of the ditch from the main fort, so the only way to retreat to the fort would be to cross that area of the ditch and enter through the sally port. That would require opening at least the small door in the main gate! Not a desirable situation.
The picture below is the entrance to the caponier at Fort Washington.
IMGP1888.JPG

This picture shows the rear of the caponier at Fort Hamilton. It stands opposite the main sally port.
IMGP5872.JPG
 

Lubliner

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So did Fort Washington really have light artillery above, behind the parapet? Two bricks thick doesn't seem to be adequate cover. Being on the east side of the Potomac below Washington I know it was lightly manned. They may have trained artillerists there (memory??).
Thanks again, Lubliner.
 

jrweaver

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It was set up for counterbattery guns; I'm not sure of the caliber but can find out from the armament lists. There is a steep gorge behind the fort, and L'Enfant didn't believe the fort needed any rear defenses. He designed the fort with an earthen closing wall. When Bernard took over the Coastal Fortifications Board he did a redesign of portions of Fort Washington, including adding the caponier on the rear of the fort. There is a spot across the peninsula housing the fort that could land troops and artillery, and Bernard didn't feel the original design properly protected that approach. This all took place well before the Civil War; it was designed to repel an attack from a foreign invader coming up the Potomac. Bernard made these changes in the 1820s.
 

Lubliner

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After Alexandria had been taken in May of 1861, it became pretty much a backwater fort. It did carry a small garrison, and I think I remember it being used as a training ground/firing practice. I hope I am remembering the right fort. My apology if I am mistaken.
Lubliner.
 

jrweaver

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The outside wall of a fort is called the scarp. Almost all Third System forts have a masonry scarp, either brick or stone. The only exception is Fort Scammel in Portland, Maine, which has a masonry-revetted earthen scarp. The scarp runs from the foundation of the fort - often a log grillage or stone - to the top of the wall. At or near the top of the wall is an overhang that keeps water from running down the face of the masonry, like a modern-day eave trough. This overhang, usually stone but sometimes brick, is called the cordon.
The following picture shows the scarp with the cordon at Fort Morgan on Mobile Point, Alabama.
View attachment 386414
Atop the cordon is the exterior slope, generally earthen, designed to absorb the impact of artillery shot and shell. The exterior slope is relatively steep, and is joined by the superior slope which continues upward at a shallower angle. The superior slope may be earthen or masonry, depending on the fort. The highest point of the superior slope is the parapet. The parapet is formed by the breast-height wall.
View attachment 386415

The picture below shows the exterior slope, the superior slope, and the parapet at Fort Monroe, Hampton, Virginia. Erosion has softened the distinction between the slopes, but they can still be seen.
View attachment 386416
The ramparts of a fort are the mass of the fort - the construction from the scarp to the parade wall. The breast-height wall forms the parapet, the highest point of the ramparts of a fort. It is behind this wall that defenders find some level of protection while defending the fort. Immediately behind the breast-height wall is the banquette, a firing step that allows riflemen/musketeers to fire over the wall. Banquette is the French term for table (think banquet), hence the elevated step. behind the banquette, the earth slopes downward at a fairly steep angle. This slope, called the banquette slope, allows a rifleman/musketeer to step backward after firing, his head now below the parapet. This allows him to reload his weapon out of site of the attacker, reloading being the longest effort in the firing process.
At the bottom of the banquette slope is the terreplein (pronounced TARE ah plin). This area is out of sight of the attacker, and allows the defenders to move freely under the protection of the parapet. The purpose of this path is to run ammunition to the guns and riflemen, and to move troops to reinforce an area or prepare for a counterattack without the attacker knowing of, or preventing, that movement.
Fort Section Graphic upper ramparts.jpg


While the banquette, banquette slope, and terreplein are generally earthen, permission was granted to pave these areas at Fort Morgan, Mobile Point, Alabama, because of the blowing sand when the pieces were fired. This preserved the the slopes, allowing the visitor to see the precise angles without the "rounding" caused by erosion at most forts.
Morgan banquette Rev01.jpg


The area behind the breast-height wall is also where the main artillery of the fort is generally located. The artillery is mounted on platforms, called barbettes. This is why the upper tier of a fort is often referred to as the barbette tier - it is the tier of guns mounted on barbettes. The barbettes shown in the above photograph are for the mounting of 360-degree carriages, carriages that will swivel the gun in a full circle. More commonly, a fore-pintle (or front-pintle) carriage is used, such as the ones in these pictures from Fort Monroe in Hampton Roads, Virginia.
Ramparts Rev01.jpg

Rampart gun positions historic Rev02.jpg


Forming the rear of the ramparts is the parade wall. This wall runs from the terreplein to the parade of the fort.
 

jrweaver

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The mass of the ramparts of a masonry fort are the casemates. Casemates are arched rooms that are most often used to house cannon. The arch has been long known as the strongest architectural form, and are used in masonry forts to bear the load of the ramparts along with barbette-mounted artillery above. To assist in spreading this weight across the foundation of the fort, a second arch, inverted, is often employed below the floor of the casemate. The picture below shows the arch above and the inverted arch below at Fort Pickens, guarding Pensacola Bay, Florida.
2-8 Pickens Inverted Arch.jpg


The arches of Fort Jefferson in the Dry Tortugas, Florida, seem to continue on infinitely.
2-12 Jefferson Arches.jpg


These gunrooms opened to outside the fort with a penetration of the scarp, called an embrasure. Embrasures could be simple openings in the wall that angled to a narrow area, called the throat of the embrasure. The idea in embrasure design was to create the smallest opening in the wall that would provide the widest field of fire of the gun. To achieve this, an iron pin with a mushroom-shaped top called a pintle was placed at the throat of the embrasure. This pin engaged the tongue of the carriage, making this the point that the gun swiveled around. In the picture below, the embrasure, the opening for the pintle, and the slot below the embrasure where the tongue of the carriage would engage the pintle.
2-3 Jefferson embrasure.jpg

Here is a gun mounted in a casemate, showing the way the carriage was mounted.
2-43 Service of Casemate Cannon Trumbull.jpg

The wheels at the front and rear of the carriage travel along iron rails in the floor of the casemate, called traverse rails. These allow the horizontal aiming of the gun.

The rear of the casemate opens onto the parade of the fort. In two early Third System forts, the openings to the parade were long, narrow galleries. These casemates were called "tunnel casemates," and provided the gunners from protection in the rear. Unfortunately, this also caused the smoke from firing the gun to remain in the casemate rather than properly venting. This practice was discontinued, and all later forts had large openings to the parade.

A tunnel casemate at Fort Pike, near New Orleans, Louisiana.
2-9 Pike Tunnel Casemate.jpg


The open-backed casemates at Fort Richmond, The Narrows, New York Harbor.
9-29 Richmond Casemates 2016.jpg


The cannon and carriage took up most of the area of the casemate, blocking the transverse arch. To run ammunition to the guns, the powder monkeys and brass monkeys would interfere with the gun crew. To solve this problem, a second set of arches, more narrow than the main arches, were created near the parade of the fort. These arches were called the monkey run, as this is where the powder and brass would be run.

The monkey run at Fort Jefferson is at the left of this picture.
12-15 Jefferson Arches 5.jpg
 

jrweaver

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Thank you! I've got one more installment - the parade and citadel. I'll try to get that out this afternoon or tomorrow, depending on my creative writing inspiration! :hungry:
 

jrweaver

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The parade of a fort is the area inside the ramparts, surrounded by the parade wall. This is the parade, not a parade ground. A parade ground is an area outside of a fort - generally dating from the Endicott Period and beyond.
The parade is a location for the drilling of troops and the performance of ceremonies. It is the location of a barracks and/or citadel, and a location for tents to supplement permanent barracks - especially during wartime.
The photo below shows the very large parade of Fort Jefferson.
12-16 Jefferson parade 3.jpg


The barracks on the parade of Fort Wayne in Detroit, Michigan.
5-2 Wayne Parade and Barracks.jpg


Some forts had a defensive barracks, called a citadel. This structure was designed as a barracks, but also a location for a last line of defense. Rather than windows, a citadel used loopholes opening to the outside. Below is a picture of the citadel on the parade of Fort Macomb (Wood).
Wood Parade.jpg

The opposite side of the citadel is the primary defensive side, the only openings being loopholes. This picture is at Fort Pike.
Pike with Citadel.jpg


Fort Morgan had a magnificent citadel that was destroyed during the siege of the fort during the Civil War.
4-4 MORGAN CITADEL AFTER ATTACK Sepia.jpg
 

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