Having obtained the plans for Robert E. Lee's campaign into the north, Major General George Brinton McClellan moved with uncharacteristic speed towards the Army of Northern Virginia. To reach his quarry, the young commander would need to move his massive army through the passes at South Mountain, just east of Sharpsburg, Maryland. General Lee would give Major General Daniel Harvey Hill, Stonewall Jackson's brother-in-law, the task of blocking the bluecoats' advance. General Hill stated after the battle, "On the 13th, I was ordered by General Lee to dispose of my troops so as to prevent the escape of the Yankees from Harper's Ferry, then besieged, and also to guard the pass in the Blue Ridge near Boons-borough. Major-General Stuart reported to me that two brigades only of the Yankees were pursuing us, and that one brigade would be sufficient to hold the pass. I, however, sent the brigades of Garland and Colquitt, and ordered my other three brigades up to the neighborhood of Boonsborough."

After a thorough reconnoiter, the Confederate general realized he would need more men to hold his ground. Hill would add, "About 7 o'clock they opened a fire upon our right, and pushed forward a large force through the dense woods to gain a practicable road to our rear. Garland's brigade was sent in to meet this overwhelming force, and succeeded in checking it and securing the road from any further attack that day. This brilliant service, however, cost us the life of that pure, gallant, and accomplished Christian soldier, General Garland, who had no superiors and few equals in the service. The Yankees on their side lost General Reno, a renegade Virginian, who was killed by a happy shot from the Twenty-third North Carolina."

General Hill, satisfied that his men at least temporarily held Fox's Gap, knew of their vulnerabilities elsewhere on the field. He reported, "There was, however, a solitary peak on the left, which, if gained by the Yankees, would give them control of the ridge commanding the turnpike. The possession of this peak was, therefore, everything to the Yankees, but they seemed slow to perceive it." However, General Robert Rodes on the Confederate far left would hold his ground. "Affairs were now very serious on our left. A division of Yankees was advancing in handsome style against Rodes. I had every possible gun turned upon the Yankee columns, but, owing to the steepness of the acclivity and the bad handling of the guns, but little harm was done to the " restorers of the Union." Rodes handled his little brigade in a most admirable and gallant manner, fighting, for hours, vastly superior odds, and maintaining the key-points of the position until darkness rendered a further advance of the Yankees impossible. Had he fought with less obstinacy, a practicable artillery road to the rear would have been gained on our left and the line of retreat cut off...The fight lasted for more than an hour after night, but gradually subsided as the Yankees retired. General Hood, who had gone in on the right with his two noble brigades, pushed forward his skirmishers and drove back the Yankees. We retreated that night to Sharpsburg, having accomplished all that was required--the delay of the Yankee army until Harper's Ferry could not be relieved."

Major General Ambrose E. Burnside, commanding the Federal 9th Corps, saw the battle with a slightly different perspective. He would report, "Early on the morning of the 14th, General Pleasonton commenced his reconnaissance of Turner's Gap and South Mountain, assisted by Cox's division, supported by Wilcox's division, of General Reno's corps, and found the enemy in force. General Pleasonton had reconnoitered the ground fully, and, after posting Benjamin's and Gibson's batteries on the high grounds immediately in front of the gap, indicated to Cox's division the road that should be taken in order to turn the enemy's right. This division and Wilcox's division became engaged immediately.

Soon after, I arrived on the ground with General Reno, and directed him to order up General Rodman's and General Sturgis' division to support Cox's division, which had passed up to the left of the main gap by the Sharpsburg road over the South Mountain. After these divisions had passed on to the front, General Reno moved on and took the immediate command of his corps. Soon after, General Hooker's corps arrived, composed of the divisions of Generals Meade, Ricketts, Hatch, and Doubleday, and I ordered it to move up to the right of the main pike, by the Old Hagerstown road, and, if possible, turn the enemy's left and get in his rear...

...The orders given to both Generals Hooker and Reno were most skillfully and successfully executed, after which General Gibbon was ordered forward just before sunset, and succeeded in pushing his command up the main road to within a short distance of the crest of the main pass, during which movement he had a most brilliant engagement after night-fall, our forces gradually driving the enemy before them.

At this time, say 8 p.m., the enemy had been driven from their strong positions, and the firing ceased, except upon our extreme left, where General Reno's division, then under command of General Cox (General Reno having been killed about 7 p.m.), were partially engaged till 10 o'clock.

My command, having been engaged for a greater part of the day upon the crests of the mountain without water, and many without food, were very much exhausted. Nevertheless they maintained their positions, and were ready on the following morning for an advance on the enemy, who had retreated in the direction of Sharpsburg during the night."