Fort Terminology

jrweaver

Corporal
Joined
Dec 9, 2020
I thought I'd do a series on fort terminology. Because the application of terms changes over time, I need to be specific that the definitions that I am using here apply to permanent fortifications of the Third System, 1816-1867. They are based on the Treatise on Permanent Fortifications that Dennis Hart Mahan used as a text in his engineering classes at the US Military Academy at West Point, as well as Scott's Military Dictionary and other period writings. Obviously these terms originated with Vauban and other engineers many years prior to the Third System, and terms differed from country to country. This is the US usage of the terms.
The terminology is French. The original texts at the Military Academy were written in French, and the first class that all cadets took when entering the academy was French. While Mahan translated these texts into English over time, the French terminology was kept. Some of the terms gradually were Anglicized - covert way became covered way, for example - but most of them remained in the original French spelling and pronunciation.
Please join in with questions, comments, and corrections! This should be fun.
I will begin with the terminology of outworks. Outworks are defined as defenses in the ditch and outside the ditch. The defenses inside the ditch are considered the main work.
 

jrweaver

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Joined
Dec 9, 2020
The term redoubt has a dual meaning. In the Third System, it is generally used to describe a strong point in advance of the main work that protects the high ground and/or provides an alarm in the event of an attack. The other meaning of the term redoubt is simply a strong point in a line of defense. By purest definition, it is an unbastioned work, but this is not necessarily the case with Third System redoubts. The redoubt at Fort Adams, for example, has two demibastions protecting the gorge.
A primary purpose of the redoubt is to determine if an attack is a reconnaissance in force or an actual attack. This allows the garrison to take appropriate action. The redoubt then is charged with slowing the attack, thus giving the main work time to prepare for a siege.
A desirable method of attacking a fort is a coup de main (pronounced KOO duh MIN), or human wave. Utilizing surprise, an attacker can storm the walls and take the fort before the garrison is prepared. It is the role of the redoubt to prevent this from happening, forcing the attacker to settle into a protracted siege.
At that point, the redoubt becomes the first line of defense in a "defense in depth." The goals of a defense in depth are to cause the siege to become a war of attrition, causing the attacker to expend time, manpower, and dollars in the attack. Ideally, this will cause the attacker to decide that taking the fort is too expensive in any one - or all three - of these categories and to give up the siege.
Redoubts were used sparingly in the Third System. Three redoubts were built, one very elaborate redoubt at Fort Adams in Newport, Rhode Island, an interesting redoubt with counterscarp galleries at Fort Hamilton guarding The Narrows between the Inner Harbor and Outer Harbor of New York City, and in the land defenses leading to Fort Monroe in Hampton, Virginia. Unfortunately, only the redoubt at Fort Adams survives.
The Advanced Redoubt at Fort Barrancas in Pensacola, Florida, does not fit the role of a redoubt. The peninsula leading to the Naval Air Station Pensacola - at that time Naval Base Pensacola - was defined by Pensacola Bay on the south and Bayou Grande on the north. Defending the only land approach to the naval base were a series of trenches anchored by two fortifications, Fort Barrancas on Pensacola Bay and the Advanced Redoubt two-thirds of the way to Bayou Grande. The Advanced Redoubt is approximately the same size as Fort Barrancas, it is not in advance of Fort Barrancas - it is in a parallel position in event of an attack on the naval base - and it has an equal mission to Fort Barrancas in event of a land attack. For these reasons, I classify the Advanced Redoubt as a fort rather than as a redoubt.
Following are pictures of the three Third System redoubts. These are excerpted from A Legacy in Brick and Stone and other sketches by author, based on drawings from NARA.

Adams Redoubt Plan Color Smaller.jpg


8-9 Redoubt Gorge Rev02.jpg


Hamilton Redoubt 2 Colorized.jpg


Monroe Aerial Redoubt Location.jpg


Monroe Redoubt Plan NARA Cleaned.jpg


Monroe Redoubt Section NARA Enhanced.jpg
 

jrweaver

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Dec 9, 2020
The glacis (pronounced glah SEE) is a long earthen slope leading to the outworks of the fort. It is cleared of all trees and obstacles, creating an open "killing zone" for an enemy advancing on the work. Ideally, the glacis is about 1,000 yards in length. Maintenance of the glacis was a principal function of the garrison when no attack was imminent.
The slope of the glacis creates a barrier in itself. The long uphill run with full uniform and accoutrements would tire the attacker, making him less efficient in his assault on the outworks.
Lack of maintenance of the glacis at Fort Gaines, defenses of Mobile Bay, was a major factor in the fall of that fort during the Civil War. Union forces were able to advance on the fort under cover of sand dunes that had not been leveled, and place mortars in the dunes within close range of the fort.
1608651046165.png
 

jrweaver

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Dec 9, 2020
The breast-height wall is a masonry revetment that forms the termination of the glacis. It provides protection for riflemen on the outworks and for gun crews if artillery is mounted on the outworks. Immediately behind the breast-height wall is the banquette (pronounced bahn KETT), a firing step. The banquette slope angles downward behind the banquette, allowing a rifleman to stand on the slope protected from fire by the breast-height wall while reloading. The covert way (pronounced KUVERT way) is a level area at the end of the banquette slope and extending to the counterscarp wall. The covert way allows troops to be moved around the outworks out of site of - and out of fire from - an attacker. This enables the defenders to move troops surreptitiously to reinforce a weak point or to prepare for a counterattack without the attacker knowing. It also allows the running of ammunition to the defenders.
1608651980080.png


1608652049792.png


1608652022529.png
 
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jrweaver

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Dec 9, 2020
The next term is straightforward, it is barbette. A barbette is simply a platform on which a gun is placed. A gun placed on a barbette is said to be mounted en barbette. The upper tier of a fort is generally referred to as the barbette tier, as the guns on this tier are placed on barbettes rather than in casemates where the carriage is mounted directly to the floor. Here are a couple of pictures of barbettes and guns mounted en barbette.
The first picture is a row of barbettes for fore-pintle carriages - carriages that swivels around a pintle that engages the front of the carriage, followed by a picture of a cannon mounted on a fore-pintle carriage and barbette.

MIMGP0240.JPG

2-46 10-inch Fore Pintle Rodman.jpg

The next picture is that of a barbette for a center-pintle carriage, one that allows a 360-degree traverse of the cannon, followed by a picture of a gun mounted on a center-pintle carriage and barbette.

MIMGP0239.JPG


2-47 15-inch Rodman.jpg
 

jrweaver

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Dec 9, 2020
The next term is traverse. It can be either a noun or a verb - I will deal with the noun first. A traverse is an earthen mound, often masonry revetted, that stands perpendicular to the line of defense. Its primary purpose is to divide the defenses along a front, preventing flanking fire down the defenses in the event that a portion is taken by an attacker and protecting gun positions from exploding shells nearby.
Traverses often have a banquette that allows rifle fire along the flank of the defenses to counter a breach in the defenses. This banquette is often near a place d'armes, defending that element.
Since a traverse is designed to block movement along the covert way and the covert way is designed to allow movement by defenders, a crochet is generally designed to allow passage around the traverse. Crochet is a French word meaning "little hook." In fortification design, it is a narrow passageway that curves around a traverse and is generally wide enough for only one person. This makes it very easy to defend, but still allows free passage single-file. The curves in the passageway prevent flanking fire down the defenses. Following are some drawings and pictures of traverses and crochets at Third System forts. The first drawing shows the defenses on one face of Fort Pike guarding the Rigolets in the defenses of New Orleans. The traverse is shown in dark green, with the brighter green crochet providing a passage around it.
Pike Plan Crochet.jpg

In the following photograph, I have colored the area of the crochet in bright green. It was originally the same height as the breast-high wall immediately behind it.
Pike Crochet Pic 2.jpg

The following drawing and photograph are of a crochet and traverse at Fort Jackson on the Mississippi River south of New Orleans. In this photograph of the crochet, the traverse is on the right and the breast-height wall of the outworks in on the left and straight ahead. This photo shows the curve that gives the name crochet to this passageway.

Jackson traverse and crochet plan.jpg

Crochet.jpg
 

jrweaver

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Dec 9, 2020
I'm sure you'll get to the definitions and differences of a redan and lunette?
By strict definition, a redan is a V-shaped, open-backed work in advance of a curtain of a fort, while a lunette is a semicircular work. The terms are often used interchangeably.
In the Third System, a ravelin is generally used in advance of a curtain, covering the entire front from bastion salient to bastion salient, it also being V-shaped. The term demilune (French for half-moon) is generally used for a semicircular work in advance of the sally port of a fort. As I had said, the engineers used the terminology they wanted! The ravelin at Fort Wayne in Detroit was called a demilune on the drawings by Montgomery Meigs, even though it was V-shaped.
The terms redan and lunette were seldom if ever used on the drawings, though they were common terms in Vauban designs in Europe.
 

Irishtom29

2nd Lieutenant
Joined
Jul 21, 2008
Location
Kent, Washington
By strict definition, a redan is a V-shaped, open-backed work in advance of a curtain of a fort, while a lunette is a semicircular work. The terms are often used interchangeably.
In the Third System, a ravelin is generally used in advance of a curtain, covering the entire front from bastion salient to bastion salient, it also being V-shaped. The term demilune (French for half-moon) is generally used for a semicircular work in advance of the sally port of a fort. As I had said, the engineers used the terminology they wanted! The ravelin at Fort Wayne in Detroit was called a demilune on the drawings by Montgomery Meigs, even though it was V-shaped.
The terms redan and lunette were seldom if ever used on the drawings, though they were common terms in Vauban designs in Europe.

By most definitions of ravelin Fort Wayne doesn't have one at all as the structure in question isn't a detached work in the ditch but is part of the glacis. Nor is it intended to give an extra layer of defense or extra shielding to a curtain but to act as a water battery. I kind of consider it a sort of very large reentrant place of arms though those don't generally mount heavy cannon. Whatever it's called it's unusual.

Demi-lune was the French term for a ravelin, triangular as they were. But going by Third System American definitions I don't know.

The lack of ravelins on bastioned Third System forts is interesting. Most ravelins in the United States are on forts built by Europeans (Ticonderoga, San Marcos, Niagara, Miamis) or by the Americans before the Third System (McHenry). What are your thoughts on that?
 

jrweaver

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Dec 9, 2020
A coverface is defined as: An earthen, earth and masonry, or masonry outwork designed to protect the scarp of a fort from siege guns. In the Third System, a coverface was implemented in various ways. In early Third System forts a coverface was integrated into the fort design to protect all faces of the fort except the seacoast fronts. Fort Morgan, guarding Mobile Bay, was a classic example of this design where the coverface protected three of the five curtains of the regular-pentagonal fort, as shown in the drawing below.
14-2 Morgan NARA drawing color captions smaller.jpg

This same concept was used at Forts Pike and Macomb, where there were two landward faces and a curved seacoast front. The coverface protected only the landward faces of the forts.
15-17 Pike Plan Colorized.jpg

A very different application of a coverface was used at Fort Monroe, in Hampton, Virginia. In this case Bernard designed a unique casemated coverface to increase the firepower on the fronts facing Hampton Roads. By using this casemated structure outside the ditch, he greatly increased the number of cannon positions impinging on the channel because of the longer front. The main fort, therefore, did not have casemates on the two primary seacoast fronts, only barbette guns that would fire over the coverface.

10-21 Water Battery Sketch.jpg


10-22 Monroe Water Battery.jpg

At Fort Warren, guarding Boston Harbor, a masonry-revetted earthen coverface was used to protect one channel front from potential siege guns on nearby islands. This coverface had seacoast guns emplaced atop the earthen coverface. Rather than casemated gun positions, the main fort opened to the ditch with rifle galleries with loopholes. Barbette guns on the main fort would fire over the coverface.

7-6 Coverface.jpg

Another interesting application of a coverface was used in two later forts of the period. Fort Taylor, guarding the anchorage at Key West, and Fort Montgomery at the US-Canadian border where Lake Champlain becomes the Richelieu River used a linear coverface to separate the island fort from the mainland. Both of these coverfaces were masonry-revetted earth. The one at Fort Taylor was not completed, and all traces have been obliterated by later construction at the site. The remnants of the coverface at Fort Montgomery are still visible, including some gun positions.
12-7 Taylor Plan Colorized.jpg



Montgomery Plan with Coverface crop.jpg

In both cases, the coverface connected to the fort with a causeway ending in a drawbridge. Additionally, the coverface connected to the land with a causeway, defended by gun positions and a banquette on the coverface.
The coverface at Fort Adams guarded the two faces of the fort facing the connection of the peninsula to the city of Newport and the rest of Rhode Island. This was the only land approach to the fort. The coverface then wrapped around the fronts facing Newport Bay, leaving the channel front as bare masonry.
8-7 Adams Plan Rev02.jpg

Note the traverses and crochets in the coverface. The Navy housing units are located on what was the glacis of the fort.
2-25 Adams Outworks Traverses.jpg


8-14 Adams Aerial Color.jpg
 

jrweaver

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Dec 9, 2020
By most definitions of ravelin Fort Wayne doesn't have one at all as the structure in question isn't a detached work in the ditch but is part of the glacis. Nor is it intended to give an extra layer of defense or extra shielding to a curtain but to act as a water battery. I kind of consider it a sort of very large reentrant place of arms though those don't generally mount heavy cannon. Whatever it's called it's unusual.

Demi-lune was the French term for a ravelin, triangular as they were. But going by Third System American definitions I don't know.

The lack of ravelins on bastioned Third System forts is interesting. Most ravelins in the United States are on forts built by Europeans (Ticonderoga, San Marcos, Niagara, Miamis) or by the Americans before the Third System (McHenry). What are your thoughts on that?
The ravelin at Fort Wayne follows the same pattern as the very large ravelin at Fort Warren - it does not guard the sally port of the fort but provides a large number of seacoast cannon to guard the two channels coming into Boston Harbor. The ravelin at Fort Wayne provides the first defense of the Detroit River, both upstream and downstream. It's location allows cannon mounted there to fire on ships well before they come into view of the fort.
The ravelin at Fort McHenry is not located in a position for land defense. It does guard the sally port, but it is an artillery position that guards the main channel into Baltimore Harbor. A landward attack on Fort McHenry would be up the peninsula to the left of the ravelin. The guns on the ravelin are not positioned to provide counterbattery fire, like the ravelin at Fort Pulaski, but to supplement the seacoast guns of the fort and coverface.
The definition of a ravelin is that it protects the curtain of a fort, not necessarily the gorge. I therefore find it difficult to separate the ravelin at Fort Wayne from other ravelins in the Third System. Just my opinion.
 

jrweaver

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Dec 9, 2020
Water battery is an often misused term. It is a command term, rather than a terminology that applies to a structure. A water battery is a group of guns under one command that are placed to defend a channel, river, or other body of water. A water battery can be located in a fort or in the outworks of a fort, and is located in some type of structure. Often the structure takes on the name water battery - this is technically not a proper usage of the term but the difference is more technical than important.
The proper terminology is the better way to express the structure. For example, the casemated coverface at Fort Monroe is called the Water Battery, even on the historical marker. The structure is a casemated coverface; the group of guns in the structure is a water battery. At Fort Morgan, on Mobile Point, there is a salient place d'armes that contained seacoast cannon and a shot furnace that is called the Water Battery. Again, the structure is a salient place d'armes and the group of guns in that structure is a water battery.

2-34 Morgan water battery.jpg
 

Irishtom29

2nd Lieutenant
Joined
Jul 21, 2008
Location
Kent, Washington
The definition of a ravelin is that it protects the curtain of a fort, not necessarily the gorge. I therefore find it difficult to separate the ravelin at Fort Wayne from other ravelins in the Third System. Just my opinion.

I go by the stricter definition that a ravelin is a detached work in the ditch protecting a curtain a curtain and/or gate.

Regards
 

jrweaver

Corporal
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Dec 9, 2020
A place d'armes is a structure in the outworks that allows the gathering of troops, primarily for a counterattack during a siege, and provides a strengthening of the outworks at a vulnerable point. A salient angle is an acute angle, and arrow pointed outward. A reentering angle is an obtuse angle, an arrow pointed inward. Both of these are considered vulnerable areas, so are often strengthened by places d'armes. Therefore, a salient place d'armes is located at a salient of the fort and a reentering place d'armes is located at a reentering angle of the fort. Following are pictures of salient and reentering places d'armes.

Fort Morgan Places d'Armes.jpg


13-4 Pickens Place darmes.jpg
 

jrweaver

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Dec 9, 2020
Crownworks and hornworks were elaborate structures that were used sparingly in the Third System, but that found application in some Civil War field fortifications. A crownwork comprises two curtains joined by a full bastion and flanked by demibastions. The only crownwork in the Third System is at Fort Adams in Newport, Rhode Island. This massive structure protects the main fort, standing in the ditch immediately in advance of the fort. It is shown in the following photograph, from NARA and colorized by the author. The crownwork is the grey structure to the right of the picture. In front of the crownwork is a tenailles. A tenailles is a structure designed to protect the masonry scarp of a fort; in this case it protects the masonry front of the crownwork. A tenailles consists of two masonry demibastions joined by an earthen curtain. The earthen curtain is designed to absorb the impact of artillery, thus protecting the masonry behind it. The tenailles stands between the bastions of the crownwork.
Adams Outworks Drwg.jpg

The following picture shows the rear of the crownwork, with counterfire galleries facing the scarp of the fort. Note the artillery positions atop the crownwork and the traverse magazine between them. These positions provided counterbattery fire up the peninsula.
Crownwork and Counterfire Galleries.jpg

A hornwork comprises a single curtain flanked by two demibastions. There is only one hornwork in the Third System, at Fort Schuyler in New York City.

Hornwork Drawing 2 smaller.jpg

The following aerial photo is from NARA, colorized by the author. The area tinted in yellow is the hornwork.

Schuyler Aerial with accents.jpg

The following picture is the drawbridge leading to the passageway through the hornwork toward the main fort.
9-9 Hornwork drawbridge.jpg


8-14 Adams Aerial Color.jpg
 
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