When the firing finally stopped on the night of December 13, the worst part of Fredericksburg began.

Thousands of wounded Union men lay scattered across the open slope in front of the stone wall, in the dark and the December cold, unable to crawl away because anything that moved in front of the wall still drew fire. They lay there through the freezing night and into the next day, crying out for water within earshot of the Confederate line, the cries thinning one by one as men died of cold and blood loss in the open. The dead lay among them, and through the night some of the bodies in front of the wall were stripped of their shoes and uniforms by Confederate soldiers who came down off the line for the warm clothing, men robbing the dead for boots while the wounded begged for water a few yards away. When a Union burial party finally reached the ground, it counted about 918 dead in front of the wall, many of them stripped bare.

The morning after the slaughter produced the battle’s most famous act of mercy, and its most famous unresolved story. According to a single later account, on December 14 a Confederate sergeant named Richard Rowland Kirkland (South), of the 2nd South Carolina at the stone wall, could no longer stand the cries from the field. He got his brigade commander Brigadier General Joseph B. Kershaw’s (South) permission to go out to the wounded, though Kershaw refused him a flag of truce, and climbed over the wall with as much water as he could carry. Out in the open, in full view of both armies, he went from one wounded Union man to the next giving them water and, by the telling, blankets and clothing, trip after trip, while both sides held their fire and watched. He has been remembered ever since as “the Angel of Marye’s Heights,” and a statue stands at the battlefield today.

The story was first written down by Kershaw in 1880, roughly seventeen years after the battle and after Kirkland himself had been killed at Chickamauga in 1863. There are no contemporary accounts of it from the time, and historians who have looked closely note that the tale may have grown in the retelling. It reaches us as a single, powerful, after-the-fact recollection, possibly true and possibly embellished, not as a verified fact. Something happened on that field that men needed to believe; whether it happened exactly as Kershaw told it seventeen years on, we cannot say.

On the night of December 14, an unusually strong aurora borealis (the northern lights, rare that far south) came up red and rippling over the battlefield. The men who recorded it in their diaries marked the strangeness of it: the northern lights hanging over a field of frozen Northern dead, as if the sky over Virginia had turned out over the men the Confederacy had killed on it. Major General Ambrose E. Burnside (North), half-broken, announced that the next day he would personally lead his old IX Corps (the large standing formation he had commanded before he was handed the whole army) in one more charge at the wall; his generals talked him out of it the following morning. On December 14 the armies simply held their positions, and a truce let the Union finally gather its wounded and bury its dead. On the night of December 15, the Army of the Potomac slipped back across the Rappahannock, took up the pontoon bridges behind it, and the campaign was over.