Lee started his Army of Northern Virginia in motion late the evening of July 4 towards Fairfield and Chambersburg. Cavalry under Brig. Gen. John D. Imboden was entrusted to escort the miles-long wagon train of supplies and wounded men that Lee wanted to take back to Virginia with him, using the route through Cashtown and Hagerstown to Williamsport, Maryland. Meade's army followed, although the pursuit was half-spirited. The recently rain-swollen Potomac trapped Lee's army on the north bank of the river for a time, but when the Union troops finally caught up, the Confederates had forded the river. The rear-guard action at Falling Waters on July 14 added some more names to the long casualty lists, including General Pettigrew, who was mortally wounded. General James L. Kemper, severely wounded during Pickett's charge, was captured during Lee's retreat.