Category Archives: American Civil War

Fortification Friday: Know your banquettes and slopes

Over the last couple of posts in this series, I’ve discussed parapets and their function.  Now let us turn to the parts of a parapet and look at those in detail.  As a refresher, this is Mahan’s profile of the parapet (highlighted line):

Parapet

Mahan defined this profile as the lines between points A-B-C-D-E-F.   It’s important to note that each individual line (defined between the points) also defines a separate component of the parapet.

Between points A and B is the Banquette Slope:

Parapet_Banquette_Slope

Specifically, point A is the Foot of the Banquette Slope and B is the Crest of the Banquette Slope.

Wait… what is a Banquette?  Mahan described the Banquette as:

The banquette is a small terrace on which the soldier stands to deliver his fire ; the top of it is denominated the tread, and the inclined plane by which it is ascended the slope.

So this explains lines A-B and B-C.  The latter being the Tread of the Banquette, and including point C, the Foot of the Interior Slope:

Parapet_Banquette_Thread

From a functional standpoint, the Banquette had to be wide enough to allow a rank or ranks of soldiers to stand in formation and work their musket.  The measure would be different depending on the number of ranks that the defender planned to use.  One rank might get by with two feet of width.  Two ranks required four feet.  So something on the order of 4 ½ to 5 feet would be preferred to allow ease of movement.  The Banquette was also given a slight slope to the interior to allow for drainage.

The Slope of the Banquette (A-B) was structured as the hypotenuse of a right triangle.  The slope would be a compromise providing support for the Tread while offering the lowest slope for the troops to climb.

One other functional requirement to consider about the Banquette is its height above the tere-plein (natural surface level), or interior, and the height of the parapet.  The troops had to be able to stand on the Banquette and shoot with most of their body protected by the other parts of the Parapet.  This governed the overall height of the Parapet somewhat, given average height of soldiers and such.

Moving further down the profile of the Parapet, we come to the Slope portion of the Parapet.  By adding point D, the Interior Crest, we have line C-D, known as the Interior Slope:

Parapet_Interior_Slope

As with the height of the Tread, this line’s length was governed by the need to allow soldiers to fire over the Parapet.  A sharp incline of this line allowed the troops space to move while keeping the mass close to their bodies.  But not being the most efficient structural support angle, that incline required careful maintenance.

Line D-E, with E being the Exterior Crest, is called the Superior Slope:

Parapet_Superior_Slope

The Superior Slope declined outward (towards point E).  This allowed soldiers to depress their weapons to engage targets directly in front of the works.  This also ensure any fires hitting the front of the fort would glance upward and away from the defenders (hopefully).  The angle of the Superior Slope was also a compromise.  Too shallow and the Parapet might be excessive and perhaps not allow enough declination for the muskets.  Too deep and the Parapet’s strength is compromised.

Continuing the same convention, the Exterior Slope is line E-F, where point F is the Foot of the Exterior Slope:

Parapet_Exterior_Slope

This portion of the Parapet had the important mission of stopping projectiles.  The preferred angle was 45º, or the natural slope at which loose dirt will pile.  Structurally, that was the best support angle for the Parapet.  Furthermore, when under fire, any dirt thrown up from the Exterior Slope would naturally fall back to that angle… one would expect.

The Exterior Slope completed the profile of the Parapet.  But there is one other part to consider, although it is not part of the defined parapet – line F-G:

Parapet_Berm

Point G is the crest of the Scarp, part of the Ditch.  Mahan called this the Berm.  The Berm connected the Parapet to the Ditch.

I have a problem with the choice of words here.  In modern context, berm is often a raised mound, almost a Parapet itself.  We spoke of “crossing the berm” in the Gulf Wars as noting a passage through defensive works thrown up in the desert.  Likewise, berms are tall, lengthy mounds built between roads and subdivisions to block noise.  And let’s not forget berms put up in front of raising flood waters.  So you see, a “berm” means some other shape to most modern readers.

But for Mahan, the Berm was a construct that allowed the weight of the Parapet to stand on something other than the back edge of the ditch (the Scarp, which we will discuss later).  Frankly, he wrote:

The berm is a defect in field works, because it yields the enemy a foot-hold to breathe a moment before attempting to ascend the exterior slope. It is useful in the construction of the work for the workmen to stand on; and it throws the weight of the parapet back from the scarp, which might be crushed out by this pressure. In firm soils, the berm may be only from eighteen inches to two feet wide; in other cases, as in marshy soils, it may require a width of six feet. In all cases, it should be six feet below the exterior crest, to prevent the enemy, should he form on it, from firing on the troops on the banquette.

Thus the Berm was a necessary evil.  It was a risk that need mitigation during construction.

These terms become very important when considering the engineering involved to build a fort.  Each component had a function. Those functions determined the measures of the line.  Engineers, being engineers, would compute those measures based on formulas provided by Mahan and others.  In short, the troops didn’t just throw this sort of thing up randomly:

They ENGINEERED it.  And that engineering involved careful study of the task using some of those terms presented above.

(Citations from Dennis Hart Mahan, A Treatise on Field Fortifications, New York: John Wiley, 1852, pages 1-3, 22.)

CSS Georgia to the surface “in chunks”; Artifacts recovered, photographed, preserved

Earlier this week, press releases from the Army Corps of Engineers updated the progress with the recovery of the CSS Georgia.  From the Stars and Stripes:

After 150 years at the bottom of the Savannah River, the armored skeleton of the Confederate warship CSS Georgia is being raised to the surface one 5-ton chunk at a time.

Navy divers who began working in late June to recover cannons, unexploded shells and other artifacts from the riverbed finally started midweek on their last major task – retrieving an estimated 250,000 pounds of the Civil War ironclad’s armored siding….

Earlier in June, the team released video of one cannon being raised out of the Savannah River.

First cannon from CSS Georgia removed

//embedr.flickr.com/assets/client-code.jsFour cannon have now gone to Texas A&M to receive treatment (Andy, any connections up there at College Station?). Throughout the summer, the Corps of Engineers has offered views of the progress on their website.  In addition they’ve posted photos of the artifacts on their Flickr page:

thrustblock_back

150615-A-SM817-070C_capsquareGrapeshot stand and cap

Bolt

And…

Profile cut of casemate

All of which has me looking forward to a day when these are conserved, preserved, and on public display.

I’m reminded of something Ed Bearss said in regard to the recovery of the USS Cairo, to the effect, “we learned how not to recover a Civil War ironclad.”  Over fifty-some-odd years, we’ve seen many advancements in regard to technique and technology in this field.  Good to see it applied in this case.  I again applaud the Corps of Engineers and the other organizations involved for taking such careful efforts to recover the CSS Georgia.

Cavalry Tactics: You better load on Sunday and shoot all week! The trooper’s load and firing line

An oft cited generalization in regard to the Cavalry during the Civil War involves the use of repeaters or breechloaders, which gave the troopers some advantage in firepower.  And often you’ll see reference to the Army Ordnance Department resisting the adoption of repeaters, citing “ammunition expenditure.”

In Cavalry Tactics, Alonzo Gray offered four vignettes to describe the nature of ammunition expenditure and the firing line.  The first came from Lieutenant Colonel George A. Purington, 2nd Ohio Cavalry.  The report cited discussed the operations of May 30, just before the Battle of Cold Harbor, where the cavalry was pushed forward to seize positions in advance of infantry movements:

… and here allow me to call your attention to the necessity of having some organized system of ordnance sergeants or men detailed, whose duty it shall be to keep cavalry commands well supplied with ammunition during engagements. Men armed with the breech-loading weapon will necessarily fire a greater number of rounds than those armed with a muzzle-loading piece, and it is utterly impossible for a cavalry man to carry more than from 60 to 80 rounds upon his person, and when dismounted and away from his horse this supply can be easily exhausted in a few hours’ firing. In this case my regiment expended its ammunition in the battle of May 31.

So once again we encounter that old equation – how much can a soldier… or in this case a trooper… carry?  In this case, the regimental commander felt that was only 60 to 80 rounds at most.

And how long would that last?  “… easily exhausted in a few hours’ firing.”

Infantry types will tell you each member of their line was limited to between 80 and 100 rounds, practically speaking – forty rounds in the cartridge box and a few other packages in pockets or haversacks.  So with good fire discipline, one might expect the “time on the line” to be roughly equal between cavalry and infantry, for a skirmish situation.

But there’s more to this than simply counting the number of bullets.  First off, where would a trooper or soldier seek resupply?  From the trains of course.  Infantry trains can normally follow close behind the line of march, save instances of forced or rapid marches.  And even then only a few hours might be expected.

Cavalry, on the other hand, might operate for days without the encumbrance of the trains.  For example, the four days that Brigadier-General H. Judson Kilpatrick’s cavalry operated towards Millen and back, November 26-29, 1864.   But of course, the trooper had a horse on which more ammunition might be carried.  Still, as Purington alludes to, the carbine was best employed on foot which put the horse out of reach.

A second problem was that not all bullets are the same.  Things that fit down the muzzle of a three-band rifle are not apt to fit the carbine slung over the trooper’s back.  The Cavalry didn’t just need any ammunition.  They needed their ammunition, as Purington continued:

At daylight details were sent to train, but no ammunition of that caliber (No. 54) could be obtained. Captain Weeks, in command of detail, with great promptness immediately started for our own train, some 9 miles distant, to obtain a supply, making trip back to Hanover Court-House, thence to Ashland, 27 miles, each man loaded with 85 pounds ammunition, in less than one half day, and even then hardly arrived in time, as three boxes were captured by the enemy before we could issue it to the men.

In one paragraph, both of the factors I mentioned above.  Half a day to haul ammunition from the trains back to the front.  Oh, and part of that was captured before the troopers could get the boxes open.  How tight was that situation?

And I feel warranted in saying that had this ammunition not arrived, and with our already too small force weakened by the withdrawal of my regiment, the consummate bravery of the brigade could not have prevented serious disaster.

Gray went on to cite another report filed a year later from Colonel Alexander Pennington, who commanded First Brigade of Major-General George A. Custer’s division during the Appomattox Campaign.  In a similar situation to Purington’s, Pennington dispatched a mounted detail to secure ammunition then distribute to the battle line at Five Forks, April 1, 1865.

As a negative example, Gray mentions that Major-General Philip Sheridan withdrew from Trevillian Station for want of ammunition.   Though one might contend that Sheridan withdrew from that battle for several reasons… the want of ammunition being just that cited with most clarity (how’s that for being kind?).

From these three sources, Gray advanced the comment:

A soldier should carry enough ammunition on his person to fight at least one battle.  A cavalryman may have ammunition on his horse, which ammunition, under most circumstances, will be available.  It will seldom be possible to bring ammunition from the squadron wagons to the firing line, but where horsemen can approach the firing line from the rear under cover, ammunition can be supplied.

On the “modern” firing line, we refer to the number of rounds carried in the tank or infantry fighting vehicle.  That determines the number of targets the unit might engage and thus the amount of time the vehicle (and crew) can remain engaged without rotation.  Of course there are other factors that I could detail here, but for the moment just focusing on the ammunition supply.  An M1A2 tank carries forty-two rounds of main gun ammunition.  The M1A2 crew might fire six or more rounds per minute, but in combat situations that would be lower for need to acquire and reengage targets.  Perhaps, in a pressed situation the crew would burn through those 42 rounds in an hour.  More likely a few hours (even then assuming continuous combat, which is not common in the modern combat environment).  After those are “sent down range” the tank is basically a mobile fortification with only machine guns. While the troopers of 1865 might be resupplied with someone dragging ammunition boxes up from the rear, an M1A1 must be loaded in a rear area where the handlers are not exposed to fire.

So, you might say this factor of ammunition expenditure and resupply is still a factor… even in a mechanized army with computerized cannon (smoothbore, mind you!) firing armor piercing ammunition.  After all 42 rounds and “a few hours’ firing” are somewhat constants for the troopers… regardless if the mount eats grass or JP-8 fuel.

Oh… and I did say Gray cited four sources, yes.  The forth was Frederick Whittaker’s Volunteer Cavalry, Lessons of the Decade.  That source deserves separate treatment … all to follow shortly.

(Citations from OR, Series I, Volume 36, Part I, Serial 67, page 895; Alonzo Gray, Cavalry Tactics, as Illustrated by the War of the Rebellion, Fort Leavenworth, Kansas: U.S. Cavalry Association, 1910, page 155.)