The Army of Northern Virginia began moving around June 18, 1863, but it did not all move at once. Lee had divided the army into four separate corps, each of which had tasks specific to it.

General Richard S. Ewell (1817–1872) commanded the Second Corps, much of which had previously been under the leadership of Stonewall Jackson. There were those who said no one could ever replace Stonewall, but Ewell came as close as anyone could. Known as “Old Bald Head” to his men, Ewell was missing a leg (he had been badly wounded at the Second Battle of Bull Run). Ewell had a wooden substitute, and he generally rode in a wagon, but he was as fierce a commander as any man could desire. The First Corps was commanded by James Longstreet, Lee’s “Old War Horse.” Ewell moved into Maryland, then Pennsylvania, well in advance of the rest of the army: his task was to forage, and, where possible, seize supplies from the enemy.