The main objective of the Union forces at Antietam was to cut off supply lines.

General George McClellan aimed to halt General Robert E. Lee's invasion of the North and disrupt the Confederacy's ability to sustain its army. By engaging Lee's forces at Antietam, McClellan sought to prevent the Confederate army from gathering resources and support from the surrounding areas. A successful engagement would not only protect Northern territory but also potentially enable the Union to reclaim strategic advantages in the war. Ultimately, this objective was part of a broader strategy to weaken the Confederate forces and secure a decisive victory.