If the gentleman's ancestor was an Alabamian, he probably served in Y. M. Moody's Brigade of Bushrod Johnson's Division. White Oak Road (Mar. 31, 1865) was one of the last times that a relatively small number of Confederates (including Moody's Alabamians) put to flight a substantially larger number of Federals. This link includes a good narrative and a map about half-way down: