Battle of Antietam

Battle of Antietam

The Battle of Antietam Creek, also known as the Battle of Sharpsburg, on September 17, 1862, was one of the most important military engagements of the American Civil War. It is known by these two names because the North named its battles after the nearest body of water, in this case, Antietam Creek, and the South chose the nearest telegraph station, or Sharpsburg.

Following the March 1862 duel between USS Monitor and CSS Virginia, Union Army major general George B. McClellan’s Army of the Potomac began a glacial advance up the peninsula formed by the York and James rivers toward the Confederate capital of Richmond. Confederate commander General Joseph E. Johnston was badly wounded during the fighting, and General Robert E. Lee took command of the Army of Northern Virginia and forced McClellan’s withdrawal. Lee was determined to strike at Union forces before they could reunite and drive south against Richmond, and during August 29–30, 1862, Confederate major generals Thomas J. Jackson and James Longstreet surprised and defeated Union major general John Pope’s new Army of Virginia in the Second Battle of Bull Run (First Manassas to the Confederates).

Pope withdrew to the defenses of Washington, and Lincoln reluctantly replaced him with McClellan, for on September 4 Lee and his Army of Northern Virginia had begun an invasion of the North. Lee hoped to cut key rail lines west and isolate Washington, with Harrisburg, Pennsylvania, as his probable objective. Southern leaders believed that a significant land victory might bring British and French diplomatic recognition of the Confederacy.

Lee’s army crossed the Potomac River and moved east of the Blue Ridge
Mountains. Arriving at Frederick, Maryland, on September 7, Lee divided his army into five separate parts, three of which were to converge on and take the major Union arsenal at Harpers Ferry. Overestimating Lee’s strength, McClellan proceeded with his customary caution; in reality, his forces outnumbered Lee’s two to one.

McClellan also fumbled away an incredible intelligence advantage. Near Frederick some of his soldiers discovered a copy of Lee’s orders, wrapped around three cigars and verified by a Union officer who identified the handwriting of Lee’s adjutant. McClellan now knew the entire disposition of Lee’s forces. Despite this, McClellan moved with the same glacial speed that had earned him the nickname “Virginia Creeper” during the Peninsula Campaign. He delayed a full 18 hours before putting his army in motion and pushing through the Blue Ridge passes. On September 14 in small intense engagements in the Battle of South Mountain and the Battle of Crampton’s Gap, Confederate forces held off the Union advance.

Lee’s army was then split in three main bodies over 20 miles. Although initially inclined to retreat on learning of McClellan’s moves, Lee decided to stand and fight. He ordered his remaining forces to join him as soon as possible and positioned his three available divisions along a low ridge extending about four miles north to south, just east of Sharpsburg and west of Antietam Creek. Hilly terrain enabled Lee to mask his inferior resources. The resultant battle was fragmented, in large part because of the terrain.

On the afternoon of September 15 the major part of the Army of the Potomac was within easy striking distance of Lee, who had only 18,000 men available. Had McClellan attacked then, Lee would have been routed. But Lee predicted that McClellan would not move that day or the next. Indeed, McClellan wanted first to rest his troops and then spent the entire day of September 16 placing his artillery and infantry and inspecting the line.

While McClellan dallied, Jackson’s corps arrived from Harpers Ferry, giving Lee 30,000 men and leaving absent only three of his nine divisions. Even with Jackson’s corps, Lee would be outnumbered 41,000 to 87,000. McClellan said after the battle that he thought Lee had 120,000 men. This is hard to believe, for McClellan planned a double envelopment to hit Lee’s flank and then smash the Confederate center.

Lee was in position to observe and command throughout the battle. McClellan remained more than a mile to the rear, unable to observe the battle in progress and with little idea of what was going on. McClellan also failed to take advantage of his superior numbers. He withheld an entire corps (20,000 men failed to see battle) and employed a piecemeal, rather than a simultaneous, form of attack. Each Union corps was committed by successive oral orders from headquarters without informing the other corps commanders and without instructions for mutual support. This process was compounded, as corps commanders sent their own divisions to the attack in piecemeal fashion. In sharp contrast, Lee gave great latitude to his subordinate commanders. McClellan also failed to employ his cavalry to cut Confederate lines of communication and prevent Confederate reinforcements from moving to the battlefield from the south. Even a delay of an hour or two might have changed the battle, because Lee’s remaining divisions arrived on the battlefield at the critical juncture, about 10:30 a.m. on September 17, with the Union attack already in progress.

The Battle of Antietam opened early on the morning of September 17 with an attack by Major General Joseph Hooker’s 12,000-man I Corps against the Confederate left held by Jackson’s corps. Hooker’s men drove the Confederates back into the West Woods. Lee called up Brigadier General John Bell Hood’s Texas Brigade, which repulsed the Union attack. Amid the smoke and ground fog, the battle lines were only 50 or even 30 yards apart. Units were destroyed as soon as they began to fight. The 1st Texas Regiment of Hood’s Brigade lost more than 82 percent of its men killed or wounded in 20 minutes, the highest loss percentage of any regiment North or South in the war. Successive Union attacks on the Confederate left by Major General Joseph Mansfield’s XII Corps and Brigadier General Edwin Sumner’s II Corps also met rebuff.

Meanwhile, at the Confederate center a crisis developed as some 3,000 Confederates under Major General Daniel H. Hill fought to hold the Sunken Road, which came to be known as “Bloody Lane.” Union major general William B. Franklin’s VI Corps mounted three separate assaults there, all of which failed. Then two  On the Union left, Major General Ambrose Burnside’s IX Corps spent the morning trying to capture a bridge over Antietam Creek. Union forces finally crossed the creek via fords, but the Confederates withdrew to higher ground. By the time Burnside was ready to renew the attack, the last division of Lee’s army, commanded by Major General Ambrose P. Hill, had arrived. Despite being exhausted from their forced march, they defeated the Union assault. The Battle of Antietam was over.

Union casualties amounted to 2,108 dead, 9,540 wounded, and 753 missing (15 percent). Confederate losses were 1,546 dead, 7,752 wounded, and 1,018 missing (26 percent). It was the bloodiest single day of fighting during the entire war. Lee waited a day and then pulled back into Virginia. McClellan failed to pursue. Lincoln was furious and soon removed McClellan from command. McClellan might have destroyed Lee on September 17 or the day after, but in the words of one historian of the battle, he was “so fearful of losing that he would not risk winning.”

This inconclusive battle nevertheless had important results. Lee’s defeat weakened Confederate hopes of securing recognition from Britain and France. Never again was the Confederacy as close to winning recognition abroad. The battle also helped ensure that the Democrats did not win control of the House of Representatives in the November elections. A 1 percent shift in the vote would have brought Democratic control and trouble for Lincoln. The Union victory also allowed Lincoln the opportunity on September 22, 1862, to issue the Preliminary Emancipation Proclamation, which as of January 1, 1863, freed all slaves in areas still in rebellion against the United States. This document transformed a war to preserve the Union into a struggle for human freedom.


Gallagher, Gary W., ed. Antietam: Essays on the 1862 Maryland Campaign. Chapel Hill: University of North Carolina Press, 1999.

McPherson, James M. Crossroads of Freedom: Antietam. New York: Oxford University Press, 2002.

Murfin, James V. The Gleam of Bayonets: The Battle of Antietam and Robert E. Lee’s Maryland Campaign, September 1862. Baton Rouge: Louisiana State University Press, 2004.

Priest, John M. Antietam: The Soldier’s Battle. New York: Oxford University Press, 1994.

Sears, Stephen W. Landscape Turned Red: The Battle of Antietam. New York: Ticknor and Fields, 1983.