The Battle of Antietam on September 17, 1862 was the bloodiest single day in American history. It resulted in a critical victory for the Union that squashed Southern hopes of gaining European support, and prompted Lincoln to issue the Emancipation Proclamation. The outcomes of the battle came from misjudgments, valor, and coincidence on both sides. In the following months, Robert E. Lee renewed Southern successes but also European interest in aiding the South, putting pressure on Lincoln to emancipate slaves as the war shifted to a focus on ending slavery.