The Antietam Campaign 17 September 1862

The Battle of Antietam on 17 September 1862 produced the single bloodiest day of the American Civil War with combined casualties of 23,000. On the ground it was indecisive, with the two armies fighting themselves to a standstill. Its repercussions would, however, prove pivotal – the Confederate Commander Robert E. Lee was forced to abandon his invasion of Maryland, which had threatened the Union capital, Washington DC. This emboldened Abraham Lincoln to issue his Emancipation Proclamation five days later, announcing that, unless Confederates laid down their arms by the end of that year, he would free all slaves not resident in Union-controlled territory. The Proclamation helped to dissuade Great Britain and France from recognizing the Confederacy. From a military standpoint, the Union Commander George B. McClellan’s overly cautious prosecution of the Antietam campaign – in particular, his refusal to pursue the retreating Confederate army across the Potomac – angered Lincoln and led to his replacement by General Ambrose Burnside. Burnside’s tenure in charge would prove brief, but a successor George Meade would defeat Robert E. Lee at Gettysburg in July 1863, generally recognized as the decisive engagement of the war.