On this day in 1862, at the Battle of Antietam, Confederate General Robert E. Lee's Army of Northern Virginia and Union General George B. McClellan's Army of the Potomac fight to a standstill along a Maryland creek on the bloodiest day in American history. Although the battle was a tactical draw, it forced Lee to end his invasion of the North and retreat back to Virginia.
After Lee's decisive victory at the Second Battle of Bull Run, Virginia, on August 30, 1862, the Confederate general had steered his army north into Maryland. Lee and Confederate President Jefferson Davis believed that another Rebel victory might bring recognition and aid from Great Britain and France. Lee also sought to relieve pressure on Virginia by carrying the conflict to the North. His ragtag army was in dire need of supplies, which Lee hoped to obtain from Maryland farms that were untouched by the war.
Lee split his army as he moved into Maryland. One corps marched to capture Harpers Ferry, Virginia, while the other two searched for provisions. Although a copy of Lee's orders ended up in the hands of McClellan, the Union general failed to act quickly, allowing Lee time to gather his army along Antietam Creek at Sharpsburg, Maryland. McClellan arrived on September 16 and prepared to attack.
The Battle of Antietam actually consisted of three battles. Beginning at dawn on September 17, Union General Joseph Hooker's men stormed Confederate General Thomas J. "Stonewall" Jackson's troops around the Dunker Church, the West Woods, and David Miller's cornfield. The Federals made repeated attacks, but furious Rebel counterattacks kept the Yankees in check. By early afternoon, the fighting moved south to the middle of the battlefield. Union troops under General Edwin Sumner inflicted devastating casualties on the Confederates along a sunken road that became known as "Bloody Lane," before the Southerners retreated. McClellan refused to apply reserves to exploit the opening in the Confederate center because he believed Lee's force to be much larger than it actually was. In the late afternoon, Union General Ambrose Burnside attacked General James Longstreet's troops across a stone bridge that came to bear Burnside's name. The Yankees crossed the creek, but a Confederate counterattack brought any further advance to a halt.
The fighting ended by early evening, and the two armies remained in place throughout the following day. After dark on September 18, Lee began pulling his troops out of their defenses for a retreat to Virginia. The losses for the one-day battle were staggering. Union casualties included 2,108 dead, 9,540 wounded, and 753 missing, while Confederate casualties numbered 1,546 dead, 7,752 wounded, and 1,108 missing.
Although the Union army drove Lee's force back to Virginia, the battle was a lost opportunity for the Yankees. McClellan had an overwhelming numerical advantage, but he did not know it. Another attack on September 18 may well have scattered the Confederates and cut off Lee's line of retreat.