To buy time for reinforcements from Major General Charles W. Field's division of Longstreet's corps to arrive and take positions on the Dimmock Line, Nathaniel Harris's brigade along with detachments from Thomas's and Lane's brigades made a stand at Forts Gregg and Whitworth while other Confederate units pulled back to or arrived at the main works. Two hundred men of the 12th Mississippi Infantry Regiment and 16th Mississippi Infantry Regiment under Lieutenant Colonel James H. Duncan of the 19th Mississippi Infantry Regiment along with artillerymen and a few troops from Lane's brigade, for a total of about 350 men, held Fort Gregg. Nathaniel Harris personally commanded the 19th Mississippi Infantry Regiment and the 48th Mississippi Infantry Regiment and a few artillerymen, totaling about 200 men, in Fort Whitworth. There were two three-inch rifled guns in Fort Gregg. Brigadier General Reuben Lindsay Walker, artillery chief of the Third Corps, removed the four rifled guns from Fort Whitworth before the Union attack because he was convinced that they would be captured by the attackers if he did not. The defenders of the forts collected and loaded extra rifles and positioned extra ammunition along the walls in preparation for the attack.