Interior of Fort Sumter

The interior of Fort Sumter, and it takes a moment to understand what is being looked at, because almost nothing here is what the builders put up.

The parade ground and the tiers of brick gun casemates are gone or buried. What fills the frame is rank upon rank of gabions — wicker cylinders packed with sand — stacked into terraces and revetted walls, with timber shoring and traverses between them. The Confederate garrison built this inside the shell of the fort while the fort was being shot down around them, working mostly at night, largely with enslaved and impressed labor brought out from the mainland.

The result was a work that could not be destroyed by artillery because it had already been destroyed and rebuilt out of the pieces. Federal gunners fired something on the order of seven million pounds of metal at this place across the siege, and at the end of it the garrison walked out under its own orders.

For anyone studying field fortification, this is one of the most instructive photographs of the war: an entire vocabulary of gabion, revetment, traverse and bombproof, built at scale, and photographed intact before it eroded away.