The Battle of Antietam (/ænˈtiːtəm/), or Battle of Sharpsburg particularly in the Southern United States, was a battle of the American Civil War fought on September 17, 1862, between Confederate Gen. Robert E. Lee's Army of Northern Virginia and Union Gen. George B. McClellan's Army of the Potomac near Sharpsburg, Maryland and Antietam Creek. Part of the Maryland Campaign, it was the first field army–level engagement in the Eastern Theater of the American Civil War to take place on Union soil. It remains the bloodiest day in American history, with a combined tally of 22,717 dead, wounded, or missing. Although the Union army suffered heavier casualties than the Confederates, the battle was a major turning point in the Union's favor.