President Abraham Lincoln at Antietam. The Battle of Antietam, Maryland, on September 17, 1862, was not the conclusive Union victory President Lincoln had desperately hoped for. Still it was enough of a win for him to issue his preliminary emancipation proclamation, which stated that on January 1, 1863, all slaves in states still in rebellion would be free. Yet in the days immediately after the battle, Lincoln became distressed at General George B. McClellan's failure to pursue Lee's retreating army. In early October, Lincoln visited McClellan at his headquarters at Antietam to urge him personally to attack.