Yes, perhaps this is a throw away post. But hear me out. Sandbags appear in many of the wartime photos from Morris Island.
Opps… yes we’ll get around to all those burst Parrott rifles in due time. But you see all those sandbags?
Dennis H. Mahan, the old instructor who wrote the manuals on engineering operations, only briefly addressed sandbags in his Treatise on Field Fortifications:
Sand bags are sometimes used for revetments when other materials cannot be procured; though their objects, in most cases, is generally to form a speedy cover for a body of men. They are usually made of canvass; the bag, when empty, is two feet eight inches long, and one foot two inches wide; they are three-fourths filled with earth, and the top is loosely tied. From their perishable nature, they are only used for a temporary purpose, as when troops are disembarked on an enemy’s coast.
In short, Mahan preferred gabions and other methods over the sandbag.
On Morris Island, the engineers worked with beach sand. If you have ever built a sand castle out on the beach, you know enough to start with moist sand. But as the sand dries, the sand starts crumbling. Major Thomas Brooks, building works against Battery Wagner and Fort Sumter in July 1863, noticed that in the basket-like gabions, the sand tended to trickle away and render the fortification useless. He turned to sandbags as an alternative. In his report he dedicated a full page just to the handling and use of sandbags on Morris Island:
In the siege operations herein considered, filled sand-bags have been used for the following purposes: Revetting parapets and embrasures, forming loop-holes for sharpshooters, filling gabions, foundations for mortar platforms, coverings for splinter-proofs and magazines, and making banquette treads and traverses. The bags have also been used for transporting sand and shell by hand.
It is hard to conceive how this siege could have been conducted without sand-bags. Forty-six thousand one hundred and seventy-five, according to the account kept at the engineer depot, have been expended on the portion of the work herein described.
In the construction of the batteries against Fort Pulaski, which were also built of sand, but few sand-bags were used. Only a small portion of that work, however, was executed under fire.
The material of the bags here used was a good quality of gunny cloth, although rather light for some of the purposes for which the bags were used. They were sewed with cotton twine. The first lot furnished had the chain-stitch; the later ones, the lock-stitch. The latter is far the best. Each bag contains .63 of a square yard of cloth, and, when finished, weighs 6 1/8 ounces.
The dimensions of the filled sand-bags, when laid, varied from 6 by 10 by 24 inches to 5 ½ by 11 by 23 inches, and contained .85 of a cubic foot of damp sand, weighing about 85 pounds; hence 32 to the cubic yard.
The bags were always laid as headers and stretchers, and usually in the English or Flemish bond.
Our experience proves that sand-bags which are tied before being laid should not be more than three-fourths filled. If full, they do not lay as well, and are more liable to burst on becoming wet or under great pressure. It is more rapid, but less economical, not to tie the bags at all, but give the throat a twist, and turn it under the end of the bag as each is laid.
Sand-bag revetting requires less anchoring to make it stand than any other. Of the reverting herein described, only that of the heavy guns was anchored by means of wires and pickets. Scarcely any of the portions not anchored failed for want of it. In the siege of Fort Pulaski, much of the hurdle and fascine reverting gave out because not properly anchored. If the sand-bag revetting of a battery which is being fought is kept wet, the sand will not so readily escape through the rents in the bags, nor will the bags burn. But this dampness hastens their decay.
At the end of two months the sand-bags used in revetting the siege works herein described began to show signs of decay; but with careful usage, under favorable circumstances, sand-bags might not require replacing in twice the above time.
Abrasion, the result of serving guns, and from other causes, made holes in the bags, which allowed the dry sand to escape, thus destroying the revetting. When the interior space would admit, sandbag revetting which had thus failed was repaired by facing it with a sod wall.
For comparison, here’s a description of sandbags from the 1940 edition of Army Manual FM 5-15, Field Fortifications:
The standard sandbag is 14 by 26½ inches flat, with an attached tie string 3 inches from the top of the bag. When filled three-fourths full, each bag weighs from 45 to 75 pounds depending upon material and weather it is wet or dry, averaging approximately 65 pounds, and fills a space approximately 4¾ by 10 by 19 inches.
More recent manuals, such as FM 5-103, Survivability, published in 1985, mention the use of acrylic fiber bags and a mix of concrete to supplement the sand’s properties. That manual also describes the use of sandbags revetting walls or repairing trenches. But the basic concept applies – a soldier with shovel stuffs sand in the bag, then places bag in the intended spot to build a fortification. However, there are some new-fangled gadgets out there which make the project much easier on the back.
Getting back to Morris Island, I think it significant, at least from the military engineering standpoint, that Brooks devoted so much space in his notes. Now I’m not proposing some monument to the sandbag. (Yet!) But we should consider the 46,175 sandbags used in the summer of 1863 when comparing to other large scale siege operations during the war.