Last week, we split all manner of hairs regarding shelters within fortifications. Some of this hair-splitting had to do with nomenclature – shot proof, shell proof, and splinter proof. And we saw that post-war writings introduced differences between facilities designated magazines and those designated shelters. We can read into this a shift in doctrine. Not only fortification doctrine, but also that of the practice of artillery. After all, there existed (and still exists) a direct relationship between fortifications and artillery.
Let us focus on the splinter proof shelter for the moment. Prior to the war, Mahan mentioned splinter proofing as a means to protect the magazine entrance. But after the war, he introduced a structure called splinter proof shelter:
Splinter proofs for trenches and enclosed works faced with timber from eight to twelve inches in diameter, and covered with a sheeting of thick boards, and from four to six feet of earth, which are supported by uprights at the back; having a board flooring as shown in the figure, have been recently used in our field works and trenches with great benefit in the saving of life.
And the illustration provided demonstrates such as structure:
Note the dimensions of the interior of this splinter proof. Eight feet tall at the entrance, slanting to six feet. Shown as 3 ½ feet wide, with a plank floor. The structure is open to the left, which would be the interior, or rear, of the line of works. And it is partially sunk into the ground, roughly three feet deep. The arrangement would protect the occupants from direct fire (from the right of view) and high angle fire (dropping on top). Being partially sunk down, some protection was afforded against shells bursting behind (to the left) of the structure. But clearly the solution balance ease of access against protection.
And notice the caption, “Shows a section of Splinter Proof used in the trenches at the Siege of Fort Wagner.” Yes, we’ve seen this sort of structure before… many times:
Looking to a handy example, right at the top is the a-a’ profile line, working from one of the splinter proofs forward through Battery Brown to the Howitzer Battery in the Second Parallel. For cross reference, this line runs through the red oval highlighted here:
A clean look at the profile:
Looking to the left, we see a slightly more elaborate splinter proof shelter, with two supporting uprights. But notice the Battery Brown splinter proof is at surface level, not sunk in.
Something closer to what Mahan illustrated stood just a few yards behind Battery Brown, indicated by profile d-d’:
The walk-space is wider than on Mahan’s diagram. But the structure generally matches. We know from reading accounts from the campaign, the intent was to provide shelter for troops staged for work on the parallels. The orientation of the trench provided protection from Confederate batteries further up on Morris Island, as well as those on James Island. The Confederate fires reaching this point of the Federal lines were typically large caliber weapons fired at higher elevations. Though not high-angle as used with mortars, which were out of range to hit these Federal trenches, the columbiad shells arrived at an angle which would normally defeat standard parapets. So a splinter proof provided some overhead protection.
So we see, documented with the maps, diagrams, and accounts from Morris Island, a shift in emphasis for field fortifications. This is not to say overhead cover was not used prior to the Civil War. Nor is it to say splinter proof shelters did not appear on earlier battlefields. What it does say is that field experience in the Civil War caused engineers to focus more attention on overhead cover, to the extent that more elaborate shelters were built. A shift in doctrine, you see.
Keep in mind, these examples come from a field army engaged in a siege. So field fortifications directed for offensive purposes, as opposed to defensive arrangements. Certainly these sort of works continued to appear on Morris Island after the fall of Battery Wagner, as the Federal presence shifted more to garrison of the hard-gained foothold in front of Charleston. But more to the point – field fortifications are “tools” that can be used for either defense or offense as the tactical situation demands. (And thus we’ll see later “lessons” from Mahan on how to build fortifications in support of siege operations.)
Writing even later, Junius Wheeler would further refine wartime experience to suggest even more elaborate shelters, in particular using wartime experience building the defenses of Washington. We’ll consult Wheeler’s lessons in turn… before then, we should consider another of those split hairs – shelters vs. magazines.
(Citation from Mahan, An Elementary Course of Military Engineering: Part 1: Field Fortifications, Military Mining, and Siege Operations, New York: John Wiley & Son, 1870, page 52.)