The Army of the Potomac crossed the Potomac River at Harpers Ferry and Berlin (now named Brunswick) on July 17-18. They advanced along the east side of the Blue Ridge Mountains, trying to interpose themselves between Lee's army and Richmond. On July 23, in the Battle of Manassas Gap, Meade ordered French's III Corps to cut off the retreating Confederate columns at Front Royal, by forcing passage through Manassas Gap. At first light, French began slowly pushing the Stonewall Brigade back into the gap. About 4:30 p.m., a strong Union attack drove the Confederates until they were reinforced by Maj. Gen. 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.