...on the Catharpin road as far as Corbin's bridge, to cover the left flank of the army. A division of cavalry, under General Custer, held the upper fords of the Rapidan; and the Third division, under General Merritt , was ordered to guard the trains assembled at Richardsville. Anticipating an attempt on the part of the enemy to check the heads of columns until he could get in position, and looking for this atta...