The Overland Campaign began as Grant's forces crossed the Rapidan River on May 4, 1864. Grant's objective was to force an engagement with Lee, outside of his Mine Run fortifications, by either drawing his forces out or turning them. Lee, displaying the audacity that characterized his generalship, moved out as Grant desired, but more quickly than Grant anticipated; Union forces had insufficient time to clear the area known as the Wilderness, a tangle of scrub brush and undergrowth in which part of the Battle of Chancellorsville had been fought the previous year. By forcing a fight here, Lee effectively neutralized the Union's advantage in artillery. He ordered Ewell's Corps to advance on the Orange Turnpike, A.P. Hill's in parallel on the Orange Plank Road, and Longstreet's from the distant Gordonsville.