On the afternoon of December 16, on Overton Hill, on the Confederate right, the war put the thing it was about into human form and sent it up the slope in Union blue.

The assault on Overton Hill was made by Major General James B. Steedman’s (North) command, and a conspicuous part of it was the 2nd Colored Brigade under Colonel Charles R. Thompson (North), three regiments of U.S. Colored Troops, the Union army’s Black regiments: the 12th, 13th, and 100th USCT. These were Black men, free and formerly enslaved, in the uniform of the United States, sent at the strongest ground on the field to help destroy the army of the people who claimed to own them. In Thompson’s own report, the hill they were ordered to take was probably the strongest works on the entire line. Defending the crest, on Major General Benjamin F. Cheatham’s (South) front, was an Alabama brigade under Brigadier General James T. Holtzclaw (South), posted behind an abatis (felled trees with sharpened branches faced outward, a barricade you have to climb through under fire) and behind that, a line of muskets waiting.

The 12th and 100th USCT led the charge, with the 13th USCT coming up in support and then charging hard. The ground funneled them: an isolated thicket bunched the regiments together as they came on, so that they took fire not just from the front but from the side, enfilading fire, raking down the length of a crowded line, which is the deadliest fire there is. They went up into it anyway. The Confederates held the hill; the assault was thrown back with terrible loss. But some of the men reached the top. As an officer of the 12th remembered it, a portion of the 13th got onto the breastworks themselves before the Confederate reserves rose up and, in his words, were able to mow down those on the works almost to a man.

The price was the highest of the whole battle. The 13th USCT, in its first major action, suffered the single heaviest regimental loss of the entire two days at Nashville: about 221 men killed, wounded, and missing out of roughly 576 engaged, near 40 percent of the regiment, many of them shot down on and at the Confederate parapet, the protective top wall of the works. Their sister regiments paid heavily too, the 100th USCT losing around 133, the 12th around 114. These were not support troops standing in reserve. They were at the hardest point of the hardest ground on the field, and they bled for it like it.

The men they were charging said so themselves. In his official after-action report, the Confederate Holtzclaw (South) described the Black brigade dashing up to the abatis and being killed by the hundreds, and wrote that he had never seen dead men lie thicker than in front of his two right regiments. That is a Confederate officer, in his own report, recording the courage of the very men his cause existed to keep in chains. From the Union side the verdict was the same. Steedman reported that he could not find that color made any difference in how his troops fought. And Major General George H. Thomas (North) himself, the Virginian who had given up his family to stay with the Union, looked over the field afterward and said, in substance, that the question was now settled, that Black soldiers would fight. Two close renderings of his exact words survive, so it sits here as his meaning rather than as a sealed quotation; the substance is well attested.

Tactically, the Overton Hill assault failed; the Confederates held the crest. But failing in the right place can still win a battle. The fury of the attack pulled Confederate reinforcements eastward, toward the threatened right, and every man Hood shifted east came off his already-paper-thin left. While the slaveholders’ army was busy holding the hill against the freedmen, the far end of its line was being stripped bare for the killing blow about to fall a couple of miles to the west.

That is the cause, made flesh and sent up a Tennessee hillside. The Confederacy existed to preserve slavery: eleven states had broken from the United States rather than accept any limit on the right to own human beings, and the Army of Tennessee in front of Nashville was the field army of that slaveholders’ republic in the West, the last one it had. The railroad and the redoubts and the hills with people’s names on them are terrain. Slavery is the reason the armies were there at all. And at Overton Hill the proof of it charged uphill in Union blue: men who had been held as property assaulting the army that held them, dying on its parapet, and winning even their enemy’s acknowledgment.