The immediate aftermath of the Battle of Antietam for Lee's army was a retreat back to Virginia.

Following the battle, which resulted in significant casualties and no decisive victory, General Robert E. Lee chose to withdraw his forces across the Potomac River. The Confederate army was battered and in need of rest and resupply after the fierce fighting on September 17, 1862. Lee's retreat marked the end of his Maryland Campaign, and although he had not been defeated in the traditional sense, the loss of momentum and resources significantly impacted the Confederacy's strategic position moving forward.