After retreating across the Potomac River at Williamsport, Maryland, Lee's Army of Northern Virginia withdrew up the Shenandoah Valley. George G. Meade's Army of the Potomac crossed the river east of the Blue Ridge Mountains and followed Lee into Virginia. On July 23, Meade ordered the III Corps, under Maj.Gen. William H. French, to cut off the retreating Confederate columns at Front Royal, Virginia, by forcing passage through Manassas Gap. At first light, French began slowly pushing Brig. Gen. James A. Walker's Confederate brigade (the Stonewall Brigade, part of Maj. Gen. Richard H. Anderson's division) back into the gap. About 4:30 p.m., a strong Union attack drove Walker's men until they were reinforced by Robert E. Rodes's division and artillery. By dusk, the poorly coordinated Union attacks were abandoned. During the night, Confederate forces withdrew into the Luray Valley. On July 24, the Union army occupied Front Royal, but Lee's army was safely beyond pursuit.