General Robert E. Lee directed Major General Lafayette McLaws to close in on the Federal garrison at Harper's Ferry via Elk Ridge, west of South Mountain. McLaws' route from Frederick took him through Middletown, where he turned southwest on the Middletown-Burkittsville Road. At Burkittsville, he marched southwest to Brownsville Pass. McLaws left Brigadier General Paul Semmes and his brigade at the western foot of the mountain at Brownsville on September 11. Semmes stayed at Brownsville until the 13th, when he moved back into the gap. Though Semmes knew of Crampton's Gap, about one mile north, he chose to occupy this position, believing any Federal thrust would follow the same route McLaws had taken. As he watched the Federal VI Corps move across Catoctin Valley, he knew there would soon be a fight for the mountain passes. Semmes sent Colonel William A. Parham's undersized brigade, the 6th, 12th, and 16th Virginia Infantry regiments, and his own 10th Georgia regiment to Crampton's Gap.
Convinced the Federals would attack Brownsville Pass, Semmes remained here and kept his own, much larger, brigade with him. He also retained the six-gun battery of Captain Basil Manly's 1st North Carolina Artillery and one gun each from the Richmond (Virginia) Fayette Artillery and the Magruder (Virginia) Light Artillery. Even as the defenders of Crampton's Gap called for help later that day, Semmes steadfastly belived the attack there was only a feint. He thought the real attack would soon turn his way. Only when the long blue lines assailed the Confederates behind the stone wall west of Burkettsville did Semmes realize his error. He then advanced several guns down the Brownsville Pass Road to strike the Federal left. Finally, he sent the 15th and 32nd Virginia and 53rd Georgia regiments down the road to help the Rebels fighting desperately along Mountain Church Road.
Semmes' reinforcements reached their objective only to find themselves behind enemy lines. They returned to Brownsville Pass without firing a shot. Semmes and his staff hurriedly road to Crampton's Gap to offer assistance but arrived just as the Federals approached the top of the gap—too late to be of any help.
(Quote): As General Semmes watched the Federals approach South Mountain, he worriedly dashed off a note to McLaws requesting reinforcements. McLaws sent him Brigadier General Howell Cobb's Georgia Brigade.
Order of Battle
Confederate States of America
Brig. Gen. Paul Semmes
10th Ga., 53rd Ga. (nc), 32nd Va. (nc), 1st N.C. Arty., Richmond (Va.) Fayete Art., Magruder (Va.) Light Art.
Col. William A. Parham
6th Va., 12th Va., 16th Va., 41st Va. (nc), Portsmouth Light Art.
United States of America
Maj. Gen. William B. Franklin, VI Corps
Maj. Gen. Henry W. Slocum
1st N.J., 2nd N.J., 3rd N.J., 4th N.J.
5th Me., 16th N.Y., 27th N.Y., 121st N.Y.(nc), 96th Pa.
Brig. Gen. Newton
18th N.Y., 31st N.Y., 32nd N.Y., 95th Pa.
Maj. Gen. William F. (Baldy) Smith
Brig. Gen. Brooks
2nd Vt., 3rd Vt. (nc), 4th Vt., 5th Vt. (nc), 6th Vt (nc)