Upon his return, Reynolds was given command of the Pennsylvania Reserves Division, whose commander, McCall, had been captured just two days after Reynolds. The V Corps joined the Army of Virginia, under Maj. Gen. John Pope, at Manassas. On the second day of the Second Battle of Bull Run, while most of the Union Army was retreating, Reynolds led his men in a last-ditch stand on Henry House Hill, site of the great Union debacle at First Bull Run the previous year. Waving the flag of the 2nd Reserves regiment, he yelled, "Now boys, give them the steel, charge bayonets, double quick!" His counterattack halted the Confederate advance long enough to give the Union Army time to retreat in a more orderly fashion, arguably the most important factor in preventing its complete destruction.