Answer:
The daylong battle was the bloodiest day of the American Civil War.
Explanation:
The daylong battle, called the Battle of Antietam by the Federals and the Battle of Sharpsburg by the Confederate forces, was fought on September 17, 1862 between the Army of Northern Virginia (lead by General Robert E. Lee) and the Army of the Potomac (lead by Maj. Gen. George B. McClellan).
Such battle resulted in 23,000 casualties, reason why it remains as the bloodiest day in American history.
