The Army of the Potomac, under the command of Maj. Gen. George McClellan, mounted a series of powerful assaults against Gen. Robert E. Lee’s forces along Antietam Creek near Sharpsburg, Maryland, on September 17, 1862. The morning attacks by the Union I and XII Corps on the Confederate left flank, and vicious Confederate counterattacks by Gen. “Stonewall” Jackson’s brigades swept back and forth through Miller’s Cornfield, across the Hagerstown Turnpike and into the West Woods. Towards the center of the battlefield, Union II Corps assaults against the Sunken Road pierced the Confederate center after a terrible struggle but failed to capitalize on their breakthrough. A third and final assault by Maj. Gen. Ambrose E. Burnside’s IX Corps pushed over a stone bridge at Antietam Creek. Just as Burnside’s forces began to collapse the Confederate right, the timely arrival of Gen. A.P. Hill’s division from Harpers Ferry helped to drive the Army of the Potomac back once more. On the 18th, both sides remained in place, too bloodied to advance. Late that evening and on the 19th, Lee withdrew from the battlefield and slipped back across the Potomac into Virginia. The bloodiest single day in American military history ended in a draw, but the Confederate retreat gave President Abraham Lincoln the “victory” he desired before issuing the preliminary Emancipation Proclamation five days later.