Walt, I found this info on the civil war soldiers and sailors system web site
Robert E. Withers (First_Last)
Regiment Name 18 Virginia Infantry
Soldier's Rank_In Colonel
Soldier's Rank_Out Colonel
Film Number M382 roll 61
18th Regiment, Virginia Infantry
18th Infantry Regiment completed its organization in May, 1861. Its members were recruited at Danville and Farmville, and in the counties of Nottoway, Cumberland, Prince Edward, Appomattox, Pittsylvania, and Charlotte. The unit fought at First Manassas under General Cocke, then was assigned to General Pickett's, Garnett's, and Hunton's Brigade. It participated in the campaigns of the Army of Northern Virginia from Williamsburg to Gettysburg except when it was detached to Suffolk with Longstreet. Later it served in North Carolina, returned to Virginia, and took an active part in the battles of Drewry's Bluff and Cold Harbor. The 18th endured the hardships of the Petersburg trenches north of the James River and saw action around Appomattox. It lost 6 killed and 13 wounded at First Manassas and in April, 1862, had 700 men fit for duty. The unit reported 206 casualties during the Seven Days' Battles, and of the 120 engaged in the Maryland Campaign, thirty-six percent of the 312 in action were killed, wounded, or missing. Many were captured at Sayler's Creek and only 2 officers and 32 men surrendered. The field officers were Colonels Henry A. Carrington and Robert E. Withers, Lieutenant Colonel George C. Cabell, and Major Edwin G. Wall.