Key Facts
- Duration
- September 4–20, 1862 (17 days)
- Casualties at Antietam
- Over 22,000 in a single day
- Confederate force size
- 55,000 men
- Union force size
- 102,000 men
- Key political consequence
- Emancipation Proclamation announced
Strategic Narrative Overview
Lee crossed into Maryland on September 4 with 55,000 men, splitting his army to capture Harpers Ferry while continuing north. McClellan, after discovering a copy of Lee's orders, pressed through South Mountain on September 14, buying Lee time to concentrate at Sharpsburg. Stonewall Jackson captured Harpers Ferry on September 15. The Battle of Antietam on September 17 produced over 22,000 casualties in a single day, with McClellan failing to commit reserves to break Lee's lines.
01 / The Origins
After defeating Union forces in the northern Virginia campaign, Confederate General Robert E. Lee sought to carry the war onto Northern soil in September 1862. His goals were to resupply his army outside the war-ravaged Virginia theater, undermine Northern morale ahead of midterm elections, and potentially secure European recognition of the Confederacy by demonstrating Confederate strength.
03 / The Outcome
Lee withdrew across the Potomac on September 18, with rearguard actions at Shepherdstown on September 19–20 closing the campaign. Although Antietam was a tactical draw, it ended Lee's strategic invasion. Lincoln declared it a Union victory and used it as the basis for announcing the Emancipation Proclamation, which effectively eliminated the prospect of British or French intervention on behalf of the Confederacy.
Belligerents & Mobilization Analysis
Side A
1 belligerent
Robert E. Lee, Stonewall Jackson.
Side B
1 belligerent
George B. McClellan.
Kinetic Engagement Axis
Scroll horizontally to view full axis. Events plotted relatively.