Fortification Friday: Stoccades as a supplemental interior arrangement

As we continue the walk through Mahan’s description of interior arrangements for fortifications, we turn next to the use of stockades.  As a defensive structure, stockades dated back to ancient times.  Stockades were quite popular on frontiers (not just the American frontier) where resources were short and adversaries were not expected to use heavy siege weapons.  As such, we tend to see more stockading in American fortifications… not just those Civil War structures we focus on here, but also for those outposts across the west.

Mahan mentioned stockades and stockading at several intervals in his instruction.  It is important to differentiate between stockading as a form of construction, in particular used for obstacles, and stockades as a defensive structure.  For reasons I cannot determine, Mahan used the archaic spelling “stoccade” to describe the latter.  And I will perpetuate that here, if for nothing else to preserve what may have been a subtle point, lost on us today.  Same material, just used in a different manner.  And toward the use of a stoccade, Mahan returned to a “… we’ll detail that later…” section of the earlier discussions.  Specifically, what to do with the back-side of those open works or on the gorge of bastions within enclosed works:

Enclosures for gorges and outlets.  A stoccade is the best enclosure for the gorge of a work.  The outline, or plan of the gorge, should be a small bastion front, for the purpose of obtaining a flank defense.

Mahan refers to Figure 39 as an example of such a plan:

PlateVIFig39

A basic lunette, but with an enclosure wall across the gorge.  I’ve taken the liberty of outlining that addition in red.  Notice how, as Mahan suggested, this is a portion of a bastion in terms of plan arrangement.  We have the curtain in the middle, a pair of flanks, and a pair of faces.  This offers a cross fire across the rear of the fortification.  Not something that would stop a determined defender.  But at least something to cause pause.

And keep in mind, this enclosure wall was not just earth.  Rather the intent was something that might be placed without heavy labor or use of precious resources.  A wood stoccade wall:

The trunks for the stoccade should be ten or twelve inches in diameter, and eleven feet in length.  It will be best to square them on two sides, so that they may have about four inches of surface in contact.  The top of the stoccade should be at least eight feet above the ground.  To arrange it for defense, a banquette is thrown up against it on the interior; the height of the banquette one foot nine inches. A strip, about two feet in length, should be cut from the top of two adjacent trunks, wit ha saw, so that when they are placed side by side there shall be an opening at top, between them, eight inches wide on the interior, and two and a half inches on the exterior; this opening, through which the muzzle of the musket is run out, in firing, is termed a loop-hole. The distance between the loop-holes should be three feet.  In this arrangement the bottom of the loop-holes will be six feet above the ground, on the exterior, to prevent the enemy from closing on them to stop them up, or to use them in the attack.

Figure 40 illustrates this arrangement:

PlateVIFig40

Notice this is across line n-m on Figure 39.  So basically across a face of the bastion.  Consider the interior arrangements described.  First, look to “n”, on the left.  We see a small banquette built as described, providing a footing for our garrison.

Consider the matching of requirement to form in the design of the stoccade wall.  The holes provided for these trunks ensured the tops extended eight feet above the ground, and thus six feet, three inches from the tread of that banquette.  Certainly sufficient to provide protection from direct fire for the man standing on that banquette.  But then we have the loop-holes, extending from the top down to six feet above the ground, which corresponds to five feet, three inches above the tread of that banquette.  So… for the guy on the inside, the loop-hole is at the right height for easy handling of a musket, through that nice little embrasure, if I may.  But… for the guy on the outside, the loop-hole is just above eye level for a man of average height and thus a little more cumbersome to reach and utilize.  Applied math!

Now what about the exterior face?

About four feet in front of the stoccade, a ditch is made twelve feet wide and three feet deep.  The earth from the ditch is thrown up against the stoccade, in a slope, to the level of the bottom of the loop-hole, to prevent the enemy from attempting to cut down the stoccade.

And we see that arrangement laid out in profile.  Again, the form matches to requirements with almost elegant simplicity.

Something easily replicated for the stage of a western movie in the 20th century.

(Citation from Dennis Hart Mahan, A Treatise on Field Fortifications, New York: John Wiley, 1852, page 60-1.)

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