Battle Spotlight #8: Antietam: Part 1 – Introduction

On September 17, 1862, the North and South clashed once more in a bloody conflict, this time on Northern soil. Antietam yielded 22,717 casualties, including 3,654 killed, and went down in history as the bloodiest day in the Civil War.


There was a long build-up to Antietam. As I explained in an earlier post, Robert E. Lee had snatched victory from the jaws of defeat during the Seven Days Campaign, where he was fighting George B. McClellan’s gigantic army along the Virginia peninsula with his back to Richmond. With his sense of strategy, quick thinking, and good subordinates like Thomas J. Jackson, he beat back McClellan and his 100,000-man army with his 70,000 men and eventually forced him to retreat and sail back up the Chesapeake to Washington.

After that, Lee faced a new challenge with John Pope’s new Army of Virginia, which was menacing his rear along the Rappahannock River. He turned and sent his army in two wings to get to the enemy. Soon, Lee’s Army of Northern Virginia was reunited near Manassas, Virginia in an inverted “V” facing Pope’s army. James Longstreet’s wing launched a surprise attack against Pope’s army and drove them into a retreat. The only thing that stopped the retreat from turning into a rout was the appearance of McClellan, who was under orders to assume command of the Army of Virginia. As the men scurried back to Washington, they cheered as they saw their beloved leader, Little Mac, coming to save them again.

Lee’s army had suffered much loss of men over the summer, but nevertheless Lee decided it was time to invade the North. He had very good reasons why. First, it was harvest season, and he needed to give the Virginia farmers a chance to collect what was left of their crops. If he took his army north, his men could be replenished with fresh food with land that war had not touched yet. Second, if they invaded the North, they could put much pressure on Lincoln to prod McClellan to defend Washington. In fact, Lee was not at all aiming for Washington – the defenses and fortifications were to strong, and by now two massive armies were sitting in the city. Lee’s real objective was the Susquehanna River, and he would draw the Union army to him. Or, if they didn’t come, he could move into Pennsylvania, Baltimore, or Washington to his discretion. Third, Maryland was a border state which had strong Southern sympathizers, and if he could convince the Maryland legislator to join the CSA, the Union capital would be surrounded by gray. And lastly, and probably most importantly, he could get foreign recognition from countries like England or France – if not only politically, also with actual military support just like during the American Revolution.

So, with those goals in mind, Lee set out for Maryland. On September 4, 1862, the advance units of Lee’s army had crossed the Potomac into Maryland. Lee’s 55,000 men were soon all in Maryland. His troops arrived in Frederick soon after and expected citizens to rush to them and see them as liberators. But reception was not as big as was expected – only a handful of people in Frederick came to them and offered them food and water, and balls held by Jeb Stuart attracted few people. This was the start of Lee’s troubles, for he had not known that while eastern Maryland had Southern sympathizers, western Maryland had more Union leanings.

Lee had another problem – Harper’s Ferry. He had expected the Union garrisons at Winchester, Martinsburg, and Harper’s Ferry to immediately surrender or retreat to the west or south, because he stood between them and the Army of the Potomac at Washington. He also assumed that once the garrisons evacuated the towns, he would have a perfect supply line running from his army down through Harper’s Ferry and to the Shenandoah Valley, the Breadbasket of the Confederacy.

But that was not so. The garrisons stayed put, under orders of General in Chief Henry Halleck to hold their ground. Meanwhile in Washington, McClellan was slowly and methodically reorganizing the two armies into one. Finally he set off towards Frederick, dividing the army in three marching wings under Generals Burnside, Franklin, and Sumner. He left two army corps to defend Washington and led the army down the winding roads including the National Road until they got to Frederick. Along the way,many friendly citizens stood outside their homes, offering pies and cakes and cool water for the soldiers. One soldier said that he hardly needed the regular army rations one day, what with all the good food provided by the citizens.

Lee decided it was worthless trying to convince the citizenry in Frederick, so he moved west. And literally, right when the last of Lee’s rear guard withdrew from Frederick, the advance guard from McClellan’s army arrived there. And this time, the citizens rushed out with joy. There was a Union banner at every window, and the townspeople all were welcoming the troops. And when McClellan arrived, there were so many people crowded around him, cheering, touching his horse and all, that he could not move.

And there, a golden opportunity came into McClellan’s hands. As an Indiana regiment laid down to rest in a field (which was yesterday the camp of a Rebel regiment), two soldiers of the XII Corps came across an envelope with three cigars, wrapped in a piece of paper. They studied over the paper and took it to headquarters. Not soon after, it ended up in the hands of McClellan. It turned out to be Special Orders No. 191, a document detailing every move that Lee was planning to make.

Lee had given very detailed instructions to his division commanders on how to deal with the Harper’s Ferry situation. His army was now west of South Mountain, a ridge that runs from the Potomac River up to Gettysburg and is about halfway between the cities of Sharpsburg and Frederick. He ordered Jackson with three divisions to march west of Sharpsburg, cross the Potomac river, double back, plow through Martinsburg, and strike the town from the southwest. Lafayette McLaws’s two divisions would take the direct route to Maryland Heights, which overlook the confluence of the Shenandoah and the Potomac Rivers and Harper’s Ferry from the north. John Walker’s division would cross the Potomac east of Harper’s Ferry and take possession of Loudon Heights, on the east. Finally, Longstreet would take three divisions and lead a supply expedition to Hagerstown. In three days, the army would again be reunited in the vincinity of Hagerstown, ready to move on to Pennsylvania.

Yes, that’s right, Lee was dividing his army into four parts in enemy territory. This was a very big gamble, one that depended on secrecy to work. But all hope of secrecy was now gone. McClellan now had everything laid out for him right on his headquarters desk. He knew the Rebel army’s plans as well as Lee himself. When Brigadier General John Gibbon of the “Black Hat” Brigade visited McClellan’s headquarters that evening, McClellan waved the paper in front of him and said, “Now I know what to do! Here is a paper with which, if I cannot whip Bobby Lee, I will be willing to go home!”

But those orders were four days old already, and McClellan would have to move very fast. The Union high command had figured out long ago that the Confederate Army could do a good deal of marching in four days.

Facing McClellan and guarding South Mountain was the division of D. H. Hill, which was so war-torn that it barely measured five thousand. Lee’s army was scattered all over the map. Now was the time to strike. And, with some delay, he did.

In the Battle of South Mountain, McClellan launched Burnside’s wing against Turner’s and Fox’s Gaps against A. P. Hill, while sending William Franklin to Crampton’s Gap which was defended by McLaws. Franklin was able to break through at Crampton’s Gap, but the Confederates held on until the very end at Fox’s and Turner’s Gaps, when they were finally overrun. It was small, but it was McClellan’s first victory against the Army of Northern Virginia. Lee finally saw his defense futile and ordered his army to Sharpsburg after his forces successfully defeated the garrison at Harper’s Ferry.

Please read my next post: Part 2 – Preparations for Battle for the continuation of the story of the Battle of Antietam!


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