Antietam: The Day That Changed the War

September seventeenth, eighteen sixty-two. The cornfields around Sharpsburg, Maryland were still standing when the shooting began at dawn. By the time it stopped at dusk, the cornfields were gone, the farmers' fences were matchwood, and somewhere between twenty-two thousand and twenty-three thousand men had been killed, wounded, or captured in a single day. No day in American military history, before or since, has produced that number of casualties in a single engagement.

General Robert E. Lee had brought approximately forty thousand Confederate soldiers north of the Potomac in September of eighteen sixty-two. It was the first Confederate invasion of Northern soil. Lee's strategic calculation was that a decisive victory on Northern ground might convince Britain and France to recognize the Confederacy and possibly intervene diplomatically or militarily. He chose to fight along Antietam Creek near Sharpsburg, where the ground offered defensible terrain and the river at his back.

General George McClellan had approximately eighty-seven thousand Union soldiers. He attacked at dawn in three separate thrusts: through the Cornfield to the north, then across the Sunken Road in the center, then at Burnside Bridge to the south. Each assault was launched sequentially rather than simultaneously, which allowed Lee to shift troops to meet each threat in turn. McClellan held a substantial reserve in place throughout the day and never committed it.

The fighting at the Sunken Road lasted roughly three and a half hours. By the time it ended, Confederate dead lay so thick in the lane that a witness wrote you could walk its length without touching the ground.

Lee held the field that night, then withdrew across the Potomac on the eighteenth. McClellan did not pursue. Lincoln was furious. He had been waiting for a Union victory that would give him political cover to issue the Emancipation Proclamation. Antietam, however terrible, was enough. He issued the preliminary Emancipation Proclamation five days later, on September twenty-second. The character of the war had changed. Confederate casualty figures from Antietam vary by source. Union losses are more precisely documented at around twelve thousand four hundred.