President Lincoln sent General McClellan in pursuit of the Confederate invaders, converging with General Robert E. Lee at Sharpsburg, Maryland. From sunrise until dusk on September 17, 1862, the Union army made repeated assaults on the Confederate lines around Dunker Church, Sunken Road, and around Burnside’s Bridge. If McClellan had thrown his entire army against all of Lee’s positions at once, the larger Union army would have overwhelmed the Confederates. By nightfall, Lee’s battered army still held its positions. McClellan had lost 12,410 men while the Confederates lost 10,318 men killed, wounded or missing. September 17, 1862 became the single “Bloodiest Day” of the Civil War. The devastating losses ended Lee’s invasion of the North and his army retreated to Virginia.