After the second battle of Bull Run, General Robert E. Lee decided to invade Maryland and Pennsylvania. On 10th September, 1862, he sent Thomas Stonewall Jackson to capture the Union Army garrison at Harper's Ferry and moved the rest of his troops to Antietam Creek. When George McClellan heard that the Confederate Army had been divided, he decided to attack Lee. However, the Harper's Ferry garrison surrendered on 15th September and some of the men were able to rejoin Lee.

On the morning of 17th September, 1862, George McClellan and Major General Ambrose Burnside attacked Robert E. Lee at Antietam. The Union Army had over 75,300 troops against 37,330 Confederate soldiers. Lee held out until Ambrose Hill and reinforcements arrived from Harper's Ferry. The following day Lee and his army crossed the Potomac into Virginia unhindered.

It was the most costly day of the war with the Union Army having 2,108 killed, 9,549 wounded and 753 missing. The Confederate Army had 2,700 killed, 9,024 wounded and 2,000 missing. As a result of being unable to achieve a decisive victory at Antietam, Abraham Lincoln postponed the attempt to capture Richmond. Lincoln was also angry that George McClellan with his superior forces had not pursued Robert E. Lee across the Potomac.

Primary Sources

(1) Carl Schurz wrote about George McClellan and Antietam in his autobiography published in 1906.

On the 17th of September, the battle of Antietam was fought, in which McClellan might have made a victory of immense consequence, had he not, with his usual indecision and procrastination, let slip the moments when he could easily have beaten the divided enemy in detail. As it was, General Lee came near being justified in calling Antietam a "drawn battle". He withdrew almost unmolested from the presence of our army across the Potomac.

(2) George Smalley, New York Tribune (20th September, 1862)

Fierce and desperate battle between 200,000 men has raged since daylight, yet night closes on an uncertain field. It is the greatest fight since Waterloo - all over the field contested with an obstinacy equal even to Waterloo. If not wholly a victory tonight, I believe it is the prelude to a victory tomorrow. But what can be foretold of the future of a fight which from 5 in the morning till 7 at night the best troops of the continent have fought without decisive result?

The battle began with the dawn. Morning found both armies just as they had slept, almost close enough to look into each other's eyes. The left of Meades reserves and the right of Ricketts line became engaged at nearly the same moment, one with artillery, the other with infantry. A battery was almost immediately pushed forward beyond the central woods, over a plowed field, near the top of the slope where the cornfield began. On this open field, in the corn beyond, and in the woods which stretched forward into the broad fields, like a promontory into the ocean, were the hardest and deadliest struggles of the day.

For half an hour after the battle had grown to its full strength, the line of fire swayed neither way. Hooker's men were fully up to their work. They saw their General everywhere in front, never away from the fire, and all the troops believed in their commander, and fought with a will. Two-thirds of them were the same men who under McDowell had broken at Manassas.

The half hour passed, the Rebels began to give way a little, only a little, but at the first indication of a receding fire, Forward, was the word, and on went the line with a cheer and a rush. Back across the cornfield, leaving dead and wounded behind them, over the fence, and across the road, and then back again into the dark woods which closed around them, went the retreating Rebels.

Meade and his Pennsylvanians followed hard and fast - followed till they came within easy range of the woods, among which they saw their beaten enemy disappearing - followed still, with another cheer, and flung themselves against the cover.

But out of those glooms woods came suddenly and heavily terrible volleys - volleys which smote, and bent, and broke in a moment that eager front, and hurled them swiftly back for half the distance they had won. Not swiftly, nor in panic, any further. Closing up their shattered lines, they came slowly away - a regiment where a brigade had been, hardly a brigade where a whole division had been victorious. They had met from the woods the first volleys of musketry from fresh troops - had met them and returned them till their line had yielded and gone down before the weight of fire, and till their ammunition was exhausted.

In ten minutes the fortune of the day seemed to have changed - it was the Rebels now who were advancing; pouring out of the woods in endless lines, sweeping through the cornfield from which their comrades had just fled. Hooker sent in his nearest brigade to meet them, but it could not do the work. He called for another. There was nothing close enough, unless he took it from his right. His right might be in danger if it was weakened, but his center was already threatened with annihilation. Not hesitating one moment, he sent to Doubleday: "Give me your best brigade instantly."

The best brigade came down the hill to the right on the run, went through the timber in front through a storm of shot and bursting shell and crashing limbs, over the open field beyond, and straight into the cornfield, passing as they went the fragments of three brigades shattered by the Rebel fire, and streaming to the rear. They passed by Hooker, whose eyes lighted as he saw these veteran troops led by a soldier whom he knew he could trust. "I think they will hold it," he said.

General Hartstuff took his troops very steadily, but now that they were under fire, not hurriedly, up the hill from which the cornfield begins to descend, and formed them on the crest. Not a man who was not in full view - not one who bent before the storm. Firing at first in volleys, they fired them at will with wonderful rapidity and effect. The whole line crowned the hill and stood out darkly against the sky, but lighted and shrouded ever in flame and smoke. There were 12th and 13th Massachusetts and another regiment which I cannot remember - old troops all of them.

(3) General Oliver Howard fought at Antietam in September, 1862. In his autobiography published in 1907, he compared the military achievements of the two opposing commanding officers, George McClellan and Robert E. Lee,

Lee's generalship at Antietam could not be surpassed; but while McClellan's plans were excellent, the tactical execution was bad. Had all of the right column been on the spot where the work was to begin, Sumner, seizing Stuart's heights by the Potomac, could have accomplished the purpose of his heart - to drive everything before him through the village of Sharpsburg and on to Burnside's front. Of course, Burnside's move should have been vigorous and simultaneous with attacks on the right. McClellan so intended. we had, however, a technical victory, for Lee withdrew after one day's delay and recrossed the Potomac.

(4) After seeing the photographs taken by Alexander Gardner at of the battle at Antietam, the writer, Oliver Wendell Holmes recorded his views on the nature of war.

Let him who wishes to know what war is look at this series of illustrations. It is so nearly like visiting the battlefield to look over these views that all the emotions excited by the actual sight of the stained and sordid scene, stewed with rags and wrecks, come back to us, and we buried them in the recesses of our cabinet as we would have buried the mutilated remains of the dead they too vividly represented. The sight of these pictures is a commentary on civilization such as the savage might well triumph to show its missionaries.

(5) Sarah E. Edmonds was present at Antietam and later wrote about it in her book, Nurse and Spy in the Union Army (1865).

How shall I describe the sights which I saw and the impressions which I had as I rode over those fields! There were men and horses thrown together in heaps above ground; others lay where they had fallen, their limbs bleaching in the sun without the appearance of burial. There was one in particular - a cavalryman; he and his horse both lay together, nothing but the bones and clothing remained; but one of his arms stood straight up, or rather the bones and the coatsleeve, his hand had dropped off at the wrist and lay on the ground; not a finger or joint was separated but the hand was perfect.

(6) Abraham Lincoln, in discussion with journalists about General George McClellan (March, 1863)

I do not, as some do, regard McClellan either as a traitor or an officer without capacity. He sometimes has bad counselors, but he is loyal, and he has some fine military qualities. I adhered to him after nearly all my constitutional advisers lost faith in him. But do you want to know when I gave him up? It was after the battle of Antietam. The Blue Ridge was then between our army and Lee's. I directed McClellan peremptorily to move on Richmond. It was eleven days before he crossed his first man over the Potomac; it was eleven days after that before he crossed the last man. Thus he was twenty-two days in passing the river at a much easier and more practicable ford than that where Lee crossed his entire army between dark one night and daylight the next morning. That was the last grain of sand which broke the camel's back. I relieved McClellan at once.