Why was Antietam a change in the strategy of the south fighting a defensive war on home territory battle of Antietam?

The Battle of Antietam marked a strategic shift for the Confederacy as it was the first significant offensive move into Union territory, aiming to relieve pressure on Virginia and gain international recognition. General Robert E. Lee sought to exploit Union weaknesses and potentially sway Northern public opinion in favor of peace. However, the battle resulted in a costly stalemate, ultimately reinforcing the Union's resolve and leading President Lincoln to issue the Emancipation Proclamation. This shift highlighted the Confederacy's struggle to maintain a purely defensive posture while seeking decisive victories to bolster its cause.