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BATTLE // September 20, 1862

Maryland Campaign

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Overview

The Maryland campaign occurred September 4–20, 1862, during the American Civil War. The campaign was Confederate General Robert E. Lee's first invasion of the Union. It was repulsed by the Army of the Potomac under Maj. Gen. George B. McClellan, who moved to intercept Lee and his Army of Northern Virginia and eventually attacked it near Sharpsburg, Maryland. The resulting Battle of Antietam was the bloodiest day of battle in American history.

Overview adapted from Wikipedia, licensed under CC BY-SA 4.0.

Significance

The Maryland Campaign of September 1862 marked Confederate General Robert E. Lee's first invasion of Union territory. Lee moved his Army of Northern Virginia north across the Potomac, prompting Maj. Gen. George B. McClellan to advance with the Army of the Potomac to intercept him. The campaign culminated in fighting near Sharpsburg, Maryland, in what became the bloodiest single day of battle in American history. McClellan succeeded in repulsing the invasion, preventing Lee from establishing a Confederate presence on Union soil. Union forces outnumbered the Confederate army by a substantial margin, though both sides suffered heavy casualties — together exceeding 44,000 men. The repulse of Lee's first northern invasion carried significant strategic weight, denying the Confederacy the kind of decisive offensive success that might have influenced foreign recognition or altered the broader momentum of the war.

Forces & casualties

Troop strength

  • United States102,234
    medium
  • Confederate States55,000
    medium

United States fielded a 1.9 : 1 numerical advantage

Casualties

  • United States28,272
    medium28% loss rate
  • Confederate States16,229
    medium30% loss rate

Commanders (2)

Confederate States

United States

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Related

6 sibling battles · 2 factions

Last verified June 2026
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