After the Battle of Antietam, the Union army captured Military plans. Specifically, they seized a set of orders from General Robert E. Lee that detailed his strategy for the invasion of the North.

This discovery provided crucial intelligence for Union forces, revealing the Confederate army's movements and intentions. The capture of these plans significantly bolstered the Union's strategic advantage and contributed to their decision-making in subsequent battles. This intelligence not only showcased the importance of information in warfare but also underscored the chaotic and unpredictable nature of battle during the Civil War.