The Battle of Antietam was fought on September 17, 1862, during the Maryland Campaign. Union forces under George McClellan attacked Robert E. Lee’s army at the Cornfield, West Woods, Sunken Road, and Burnside Bridge. Although the battle ended without a decisive tactical winner, McClellan stopped Lee’s advance, making Antietam a strategic Union success. The battle caused nearly 23,000 casualties and led President Abraham Lincoln to issue the Preliminary Emancipation Proclamation five days later.