The battle was over by 5:30 p.m. On the morning of September 18, Lee's army prepared to defend against a Federal assault that never came. After an improvised truce for both sides to recover and exchange their wounded, Lee's forces began withdrawing across the Potomac that evening to return to Virginia. Losses from the battle were heavy on both sides. The Union had 12,410 casualties with 2,108 dead.^[42] Confederate casualties were 10,316 with 1,547 dead. This represented 25% of the Federal force and 31% of the Confederates. Overall, both sides lost a combined total of 22,726 casualties in a single day, almost the same amount as the number of losses that had shocked the nation at the 2-day Battle of Shiloh five months earlier. The fighting on September 17, 1862, killed 7,650 American soldiers.^[43] More Americans died in battle on September 17, 1862, than on any other day in the nation's history. Antietam is sometimes cited as the bloodiest day in all of American history. Antietam ranks fifth in terms of total casualties in Civil War battles, falling behind Gettysburg, Chickamauga, Chancellorsville, and Spotsylvania Court House.