The Battle of Antietam gave the Union a morale boost and demonstrated that Confederate forces could be repelled on Northern soil. The Emancipation Proclamation, issued shortly after the battle, shifted the war's narrative toward abolition. The battle also discouraged European powers from recognizing the Confederacy, which was important for the Union's diplomatic efforts. Additionally, the battle provided President Abraham Lincoln with a window of opportunity to issue the preliminary Emancipation Proclamation, which changed the war's focus by highlighting the Union's commitment to ending slavery.