After Antietam, Lee's army was retreating back across the Potomac River at Boteler's Ford, about 1 mile east of Shepherdstown. Brigadier general William N. Pendleton, an ordained Episcopal minister before the war, was given command of the rearguard at Boteler's Ford covering the withdrawal of the Army of Northern Virginia back into Virginia. He was Lee's chief of artillery. As such he would dispatch various artillery units to other commands. But he had never commanded troops himself.