The Battle of Antietam took place on September 17, 1862, during the American Civil War as part of the Maryland Campaign. It represented a significant moment in the Eastern Theater, as it was the first field army–level engagement of the war to occur on Union soil. Major General George B. McClellan's Union Army of the Potomac had pursued Confederate General Robert E. Lee's Army of Northern Virginia into Maryland, setting the stage for this major confrontation near Sharpsburg, Maryland, and Antietam Creek.
The engagement began at dawn on September 17 when Major General Joseph Hooker's corps mounted a powerful assault on Lee's left flank. The fighting was intense and wide-ranging, with attacks and counterattacks sweeping across Miller's Cornfield and swirling around the Dunker Church. The Union Army, under McClellan's command, launched successive attacks against Lee's army, who held defensive positions behind Antietam Creek. The battle involved complex maneuvers and sustained combat across multiple sectors of the battlefield.
Although the Union Army suffered heavier casualties than the Confederates, the battle proved to be a major turning point in the Union's favor. The engagement remains the bloodiest day in American history, with a combined tally of 22,726 dead, wounded, or missing on both sides. This heavy toll underscored the intensity and scale of the combat, and despite the Union's greater losses, the strategic outcome represented a significant moment in the course of the Civil War and the Union's ultimate military prospects.
The American Civil War (1861–1865) was the deadliest conflict in American history, killing an estimated 620,000 to 750,000 soldiers and an unknown number of civilians. The Confederate States of America, formed by eleven seceding Southern states, faced the Union in four years of warfare across 23 states and territories. Major engagements included First and Second Bull Run, Antietam (the bloodiest single day in American history, September 17, 1862), Chancellorsville, Gettysburg (July 1–3, 1863), Vicksburg (surrendered July 4, 1863), and Sherman's March through Georgia and the Carolinas (1864–1865). President Lincoln issued the Emancipation Proclamation on January 1, 1863, transforming the war's stated purpose to include the abolition of slavery and enabling the enlistment of approximately 180,000 Black men in the United States Colored Troops. Confederate General Robert E. Lee surrendered to Ulysses S. Grant at Appomattox Court House on April 9, 1865. The war resolved the question of secession and ended American slavery, though Reconstruction would face sustained resistance in its attempt to secure civil rights for formerly enslaved people.
22,726 dead, wounded, or missing on both sides combined
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