Field Fortifications

jrweaver

Corporal
Joined
Dec 9, 2020
First, I'll post a caveat. This is not my primary area of study, and therefore I have not spent a lot of time looking at field fortifications. I have, however, spent some time with Dennis Hart Mahan's Treatise on Field Fortifications, and have climbed around a number of earthwork forts. Using those tools, I'll attempt to describe earthwork fortifications as a contrast/comparison to masonry fortifications. Comments and corrections from the readers will be greatly appreciated.

A significant difference between an earthwork fortification and permanent fortification is in the outworks. The outworks of an earthwork fort are often nonexistent, with the exception of the ditch. The excavation of the ditch not only increases the effective height of the scarp, but it also provides the earth for the ramparts of the fort. While there is not usually a sloped glacis, the area in advance of the fortification is usually cleared of all trees and other obstructions - in the same manner that a glacis is cleared in advance of a permanent fortification.

The other outwork that often is constructed in advance of a field fortification is an abatis. An abatis is an entanglement of sharpened branches that greatly slows the advance of an attacker, leaving the attacker under the cannon and riflery of the fort for an extended period of time.

The exterior slope of an earthwork fortification generally follows the natural angle of the earth, and thus varies in the angle of the slope. The natural angle of clay, for example, is much steeper than the natural angle of sand. Unless a revetment is used to steepen the angle, the natural angle of the material dominates. To protect the slopes, and if time permits, the slopes are sodded to add a level of permanence.

The exterior slope in an earthwork replaces the scarp in a permanent fortification. It runs from the ditch to the superior slope, which provides the parapet. This can be equivalent to, or at least analogous to, these works in a permanent fortification. At the parapet, a vertical slope, called the interior slope, descends to the banquette. While this slope can be earthen, for the practical reason that a rifleman/musketeer would prefer to stand against this slope, it is usually revetted with wood - generally making it a vertical wall. This wall is often called the breast-height wall, as in permanent fortifications.
The banquette and banquette slope are the same as in permanent fortifications.

In plan, field fortifications use the same shapes as permanent fortifications. Salients (acute angles) are used facing the attacker, and flanks are used for enfilading fire. Bastions are generally used in the same manner as permanent fortifications, although the flanking fire is from the parapet rather than from casemates as in masonry fortifications. The same angles used in permanent fortifications to eliminate any areas of the ditch that would not be under fire (dead space) are used in earthen fortifications.

The curtains of earthen fortifications - the walls between the bastions - are identical in function to those in permanent fortifications.

A field fortification may have a terreplein that is at the base of the banquette slope, or the banquette slope may terminate at the parade, depending on the height of the ramparts. To minimize excavation, the parade is generally at the level of the country.

I will follow this post with some illustrations of field fortifications. I hope it was helpful.

An abatis in advance of the fort.
Abatis.jpg


The ditch and exterior slope

Exterior Slope and Ditch.jpg


Two bastions joined by a curtain, from inside one bastion
Bastions and curtain.jpg


Wooden revetments at breast-height wall.
Wooden Breast Height Wall.jpg


The covert way at a water battery
Covert Way at Water Battery.jpg


The sally port of a field fortification is generally quite primitive, comprising simply a wooden gate. Flanking defense is provided by bastions adjacent to the curtain with the sally port.

Sally Port.jpg


Unlike masonry fortifications, embrasures were generally open-topped and often wood-revetted, like those shown here. In other cases, no embrasures were used - the guns were simply mounted to fire over the parapet.
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Lubliner

Captain
Forum Host
Joined
Nov 27, 2018
Location
Chattanooga, Tennessee
I have found so far two instances when the Union strung wire from stumps in front of their entrenchments; one at Fort Sanders in Knoxville, and the second with Meade or Butler near the James River, in 1864.
Also I recommend this book for a detailed look into building some of the works with artillery around Charleston. It has diagrams, and the vocabulary is quite technical, as to mathematical trajectories and timed fuses. The red covered hard back is the best buy.
Siege Train: The Journal of a Confederate Artilleryman in the Defense of ... - Edward Manigault - Google Books
I am really enjoying your photographic displays along with the word description.
Lubliner.
 

jrweaver

Corporal
Joined
Dec 9, 2020
Fort Meigs is a War of 1812 fort that mixes earthworks with a wooden palisade. It was built well before the Civil War, but the technology applies. Here is a series of pictures of the features of the fort.

This is a plan of the fort. Rather than bastions, this fort uses wooden blockhouses to provide flanking fire along the palisades.
Plan of Fort from display.jpg

The river that the fort controls is in the upper left of this picture. Note the batteries along this portion of the fort. There is a steep slope down to the water, so land defenses on this side are abbreviated - thus only three blockhouses. The remaining fronts have the majority of blockhouses, relatively closely spaced. This is because of the short range of the flanking cannon and the very large size of the fort.

Note the Grand Traverse through the middle of the fort, designed to prevent fire on the reverse side of the fort. This earthen mound is, in actuality, not a traverse, but a parados. A parados mirrors the function of a traverse, but runs parallel to the face of a fort rather than perpendicular to them.

Below is a picture of the parados of Fort Totten, Throgg's Neck, northern defenses of New York City. Because of the height of the masonry fort, the parados is much taller than the parados at Fort Miegs.
9-17 Totten panorama from parados.jpg
 

Irishtom29

2nd Lieutenant
Joined
Jul 21, 2008
Location
Kent, Washington
Common in field fortifications were fraises, inclined or horizontal sharpened stakes (also called storm poles) and palisades, an obstruction of vertical stakes. Both can be seen in these photos, one of a redoubt at the Yorktown NPS park (top) and the other of fortifications at Atlanta in 1864.

A dense abatis can be seen on the left of the Atlanta photo.
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Irishtom29

2nd Lieutenant
Joined
Jul 21, 2008
Location
Kent, Washington
Stockades were also placed behind the parapets of the covered ways of permanent fortifications but these are seldom seen on old forts now because of rot. Even in the old days such palisades were often only erected in wartime. The last time I visited Fort Ticonderoga and the reconstruction of Fort Stanwix (below), both in New York state, they had palisaded covered ways.

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The tips of the palisade can be seen in this photo of Fort Stanwix. Note how the glacis covers the lower part of the wall from cannon fire.

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jrweaver

Corporal
Joined
Dec 9, 2020
At Fort Stevens on the Columbia River, there was a Third System battery that was wood-revetted. To preserve the materials, they used concrete instead of wood. Since Fort Stevens is mostly an Endicott Period fort, it is confusing for the non-fortnerd to understand what was Endicott and what was Third System/Civil War era. I was very disappointed in that decision.
 

Lubliner

Captain
Forum Host
Joined
Nov 27, 2018
Location
Chattanooga, Tennessee
At Fort Stevens on the Columbia River, there was a Third System battery that was wood-revetted. To preserve the materials, they used concrete instead of wood. Since Fort Stevens is mostly an Endicott Period fort, it is confusing for the non-fortnerd to understand what was Endicott and what was Third System/Civil War era. I was very disappointed in that decision.
Similar problems occur with Naval vessels. Not many nonnerds know what Ellet refers to and think 'monitor' is strictly Ericsson's creation. Oh how I wish I was a nerd!
Lubliner.
 

Jpcavinder

Cadet
Joined
Dec 14, 2020
Were there times that the exterior slope wasn’t used? I’ve seen a couple of reenactment areas that don’t have them while most I’ve seen do have them.
 

jrweaver

Corporal
Joined
Dec 9, 2020
Yes, there were a number of masonry forts that did not have an exterior slope, and quite a few field fortifications that didn't have an exterior slope. In field fortifications, the scarp, being earthen, served as both the scarp and exterior slope.
 

jrweaver

Corporal
Joined
Dec 9, 2020
Fort Trumbull, in New London, CT, did not use an exterior slope.
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Likewise, Fort Schuyler did not use an exterior slope. Uniquely, it used a crenelated wall at the parapet on the faces of the primary and secondary seacoast fronts.
9-5 Schuyler Scarp.jpg

Fort Washington, a transitional work between the Second and Third System, used only a superior slope.
IMGP5665.JPG
 
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