Fortification Friday: Bomb Proof shelters, as in “force protection”

Last week I pointed to a change… if we may, an evolution… in military practice based on experiences of the Civil War.  In that case, we saw a new class of “semi-permanent” fortifications introduced.  And beyond that, we saw several improvements and refinements of the facilities constructed for fortifications, be those temporary or semi-permanent.

Now let us look at another evolution, just as subtle.  But one I would submit was a major change in the function of fortifications.  In his 1870 instructions, Mahan moved immediately from discussion of magazines into a similar structure with different function:

Bomb Proof Shelters.  Bomb and splinter proof shelters of wood have also been carefully built in the interior of some of these enclosed works, and in the gorges of those open to the rear; both may be arranged with loop-holes for defense. These are mostly constructed in the manner shown in Fig. 39, bis.

This brings us back to reference the shelter built on Morris Island the shelter built on Morris Island in the summer of 1863:

MahanFig39bis

As related before, this was not necessarily a “new” structure.  Rather this was the use of a type of structure in a different manner, addressing an evolving requirement on the battlefield.  In this case, on Morris Island, the requirement was protection from shells and shrapnel delivered from high-angle or, as Mahan called it, curved, fires (or as I sometimes relate – fires acting on the vertical plane).  Overhead cover, we’d call it today.

Mahan gave a general description as to the construction of these shelters:

The exterior side is of heavy logs placed in juxtaposition, resting on a ground-sill and capped at top.  Parallel to these is another row, which may also be in juxtaposition or at short intervals apart and capped like in the outside row.  The roofing, consisting of heavy logs laid in juxtaposition and covered by thick jointed boards, rests on the capping.  The back face may be sealed on the inside to obviate the dampness from the earth resting against the back; and some simple method of drainage, by fascines or tiles, is arranged to carry off the water from the earthen covering.  This last should be the same as for the powder magazines.

So, these shelters were “like” magazines, but were not magazines.  The purpose of these shelters was to protect the troops, supplies, and equipment.  We’d call this force protection today.

But there is scant mention of this in the pre-war courses.  Here’s what I think (as in my thoughts… make sure you don’t get the idea I’m putting words in Mahan’s mouth…) – prior to the war, doctrine did not envision a situation where a field army would remain in postion subject to prolonged attriting fires.  Prolonged, as in more than a few hours.  Yes, things like mortars and howitzers existed prior to 1861.  And yes, during battle armies would be subject to fires from those type of weapons.  But, prior to 1861, the general perception was that sort of exposure would be limited, depending on the situation.  Perhaps only in a situation where an army was preparing a large scale assault… or preparing to receive a large scale assault.  So such exposure would be limited to a phase in a particular battle.

However, wartime experience brought with it a new perspective.  Entire campaigns would be fought with soldiers almost constantly in contact and exposed to attriting fires.  For emphasis, let’s just say in 1861, William T. Sherman led his command toward Manassas with the notion his troops would only be under fire (save some minor delaying actions) for a limited period of time on the battlefield.  But in 1864, he led a much larger force through Northern Georgia fully expecting the troops to be under fire every single waking hour.  An army could no longer afford to simply “lay in the open” waiting for the signal to attack. That wait might be for days, if not weeks.  And the artillery, of both sides, would not be idle.  We can offer many reasons this change occurred.  Regardless of cause, the effect was a need for better protection of the force.

Applied to practice of field fortifications, this brought a need for structures that would afford relief to the infantry.  Again, this is not to say such shelters did not exist prior to 1861.  Rather, such shelters were of little concern, prior to the war, for those constructing temporary, field fortifications.  However, by the summer of 1863, witnessed on Morris Island, these structures became necessary.  So much that a significant amount of manpower was diverted from other tasks in order to ensure “force protection” was given as the siege lines advance.  Oh… and so much that the defenders in Battery Wagner spent more time on shelters than on erecting more batteries.

And speaking of the defenders, Mahan added, with respect to the shelters:

It is highly important that these works should be so organized as to afford a retreat for the garrison should the main work be carried.  This might be done in some cases, by masking, with earth, only the lower portion of the side looking on the interior of the work, and covering the exposed timber with iron plating with loop-holes, to sweep all the interior space.

This sounds very much like a safety redoubt or keep…. but “sounds like” is not “the same as” in this case.  In his pre-war writing, Mahan proposed safety redoubts and keeps for field fortifications.  And he retained, those designations, even going further to elaborate on the construction of blockhouses as a form, even when proposing these shelters with arrangements for retreat.  The difference between here is the employment.  The keep was intended for a fortification with large interior capacity and for use as a last line of defense.  The shelters described, in the paragraph above, were employed even in smaller fortifications and were not necessarily the “last line” to defend.  The point being – shelters would protect the soldiers AND offer them a position from which to fight in conjunction with the localized defense within the fortification.  A keep was a shelter from which to rally and reform for the final defense of the entire fortification.

Not quite the trenches of World War I.  But the concept was in the air.

(Citations from Mahan, An Elementary Course of Military Engineering: Part 1: Field Fortifications, Military Mining, and Siege Operations, New York: John Wiley & Son, 1870, page 54-5.)

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