The Battle of Antietam was a pivotal encounter in the American Civil War, taking place on September 17, 1862, near Sharpsburg, Maryland. General George B. McClellan, commanding the Union Army of the Potomac, confronted General Robert E. Lee's Army of Northern Virginia, which had crossed into Maryland in an attempt to gain a decisive victory on Northern soil. This battle was characterized by its brutal combat, with fierce engagements spread across several key locations such as the Cornfield, the Sunken Road, and Burnside's Bridge.

The battle commenced early in the morning and progressed throughout the day, with both sides suffering heavy losses. Approximately 23,000 soldiers were killed, wounded, or missing by the end of the day, making it the bloodiest single day in American military history. Despite the immense casualties, neither side achieved a clear victory, but McClellan's forces effectively halted Lee's advance, causing him to retreat back into Virginia.

The aftermath of Antietam was crucial as it gave President Abraham Lincoln the opportunity to issue the Emancipation Proclamation, which transformed the Union war effort into a battle against slavery. This strategic shift not only strengthened Northern resolve but also had significant implications for the future of the Confederacy. Additionally, the battle highlighted the need for improved military strategies and tactics as both sides learned from the fierce engagements of the day.