The Battle of Antietam, September 17, 1862

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Today in 1862, the Battle of Antietam took place between Union and Confederate forces near Sharpsburg, Maryland. This battle represented a turning point in the Civil War, for it marked the beginning of the Confederate retreat from its first invasion of the North.

Robert E. Lee's Army of Northern Virginia was a 45,000-man strong force when it entered Maryland after their victory at the Second Battle of Bull Run. General Lee hoped to find supplies and recruits in Maryland, which had a large number of Southern sympathizers living within its borders. He also wanted to strike a blow at Northern morale by showing that Confederate forces could push into Northern states with impunity. The residents of Maryland were not won over the to the Southern cause, however, and Maryland would stay in the Union camp for the remainder of the war.

The Army of the Potomac, under the command of US General George McClellan, was tasked with intercepting Lee's forces before they had the chance to escape back into Virginia. During their advance, two Union soldiers from the 27th Indiana Volunteer Infantry found a document wrapped around three cigars. The document turned out to be Special Order 191, the detailed battle plans of the Confederate Army of Virginia. General McClellan learned from the document that Lee had divided his forces, a move that left them even move vulnerable to defeat against the Union's larger numbers. Amazingly, McClellan waited 18 hours before acting on this information, which was enough time for some of Lee's forces to arrive at Antietam Creek and begin building defenses behind it. Had McClellan acted quickly and decisively, it is possible that the Confederate force could have been routed easily. As it was, Lee had only 18,000 men at Antietam.

Union forces began arriving near Lee's lines on September 15th, but General McClellan waited more than a day to press an attack. Part of the delay was due to his overly cautious nature; the other part is owed to his belief that Lee commanded more than 100,000 men. McClellan ordered a probing attack on the evening of the 16th, which attracted Lee's attention and told him that the Union forces intended to concentrate on his left flank. He shifted men and waited.

For the sack of brevity, we will not discuss the details of the next day's engagement. Suffice it to say that McClellan show his lack of imagination once again and failed to give his top commanders any information as to his overall battle plan. Instead, each subordinate general was only given orders for his area of responsibility. Because of this, the Battle of Antietam was actually three separate battles. Confusion was rampant and it was estimated after the battle that 1/3 of the Union troops present never fired a shot due to the fact that they were never positioned properly. The North's advantage in manpower and artillery was at least partly nullified.

The battle ended by early evening. The Southern forces had over 10,000 casualties with 1,546 dead. The Union forces faired even worse with 12,400 casualties and 2,108 dead. Since both sides of the fight were Americans, the Battle of Antietam was and remains the most deadly day in United States military history. This includes such epic battles as the D-Day invasion of Normandy and the assaults on Iwo Jima and Okinawa during the Second World War.

Lee's forces began retreating back to Virginia on the evening of the 17th. Despite requests from the War Department that he do so, General McClellan failed to pursue the Confederate forces into Virginia. He claimed that he was short of supplies and did not want to over-extend his forces. While this may have been true, forces under General Lee, while constantly lacking adequate supplies of every type, remained an effective fight force until the very last months of the war. After visiting McClellan later in the month, Lincoln came to the conclusion that his top general was too cautious to be effective. He relieved McClellan of his command on November 7.

Technically, the Battle of Antietam was a strategic victory for the Union only because Lee withdrew his forces from the battlefield first and ended his invasion of Maryland. Although no one on the field of battle knew it at the time, the battle also allowed President Lincoln to issue the Emancipation Proclamation (which freed slaves still held in bondage) on September 22, even though it did not go in effect until January 1st, 1863. Lincoln had been waiting to make the announcement until after a significant Union victory so that it would not be seen as a desperate effort to win support of European nations, especially England and France, who were still on the fence with regard to recognition of the Confederacy.

Today, the Antietam National Battlefield covers over 3,200 acres, most of the area in which the battle took place.