Battle of Antietam

Battle of Antietam, important battle of the American Civil War. The Battle of Antietam was the bloodiest one-day battle in all of United States history. It was one of the most important battles of the Civil War because the Confederate defeat led General Robert E. Lee to abandon temporarily his plans for an invasion of the North and because it discouraged both Britain and France from coming to the aid of the Confederacy. The Union victory also led President Abraham Lincoln to issue the first, or preliminary, Emancipation Proclamation, in which he declared his intention to free all slaves in the rebel states.

After the Second Battle of Bull Run, Lee decided to invade Maryland. Although he knew that he could not successfully attack Washington, D.C., he wanted to move the fighting out of war-torn Virginia, and he wanted to interrupt the North’s supply lines. In addition, he thought that a success in the North might lead France or Britain to recognize the Confederacy. Lee moved across the Potomac River with his entire army of about 50,000 troops and then sent the majority of his army under General Stonewall Jackson to Harpers Ferry. They were to seize the area and open up supply routes to the Shenandoah Valley. Lee then stationed the rest of his army at Sharpsburg, Maryland, near Antietam Creek.

Lee’s forces were intercepted on September 17, 1862, at Antietam Creek by a Union army of 75,000 men under the command of General George Brinton McClellan. The fighting began the same day. Despite the superior number of Union forces, the Confederate Army was able to hold off the Union troops. Just as Union General Ambrose E. Burnside captured a bridge and led his men across the creek, a Confederate force led by Ambrose P. Hill arrived with fresh reinforcements for Lee. The Union attack was repulsed, and the fighting stopped. Lee led his men in orderly retreat back to Virginia, and the North did not pursue him. Both sides had lost heavily, with total Union casualties of about 12,500, including 2,108 dead, and Confederate casualties of about 10,500, including at least 2,700 killed. The casualties were so high that Antietam was the bloodiest one-day battle of the Civil War (and in all of U.S. history).

Although the outcome of the fighting was indecisive, Antietam was a major success for the Union. As a result of the battle, Lee lost almost 25 percent of his men and gave up his plan to invade the North. Diplomatically the Confederate defeat at Antietam made it more difficult for France or Britain to openly support the Confederacy. Prior to the battle, Lincoln had informed his cabinet that he intended to free the slaves in states that were in active rebellion. However, the cabinet had persuaded him to wait until a Northern victory so it would not seem like a desperate measure. Antietam served that purpose. Five days after the battle, on September 22, Lincoln issued the first, or preliminary, Emancipation Proclamation.

The area where the Battle of Antietam took place was designated a national battlefield site in 1890. See also Antietam National Battlefield.