Lt. Gen. Jubal A. Early's Confederate force crossed the Potomac River into Maryland on July 5, 1864, after moving north into the Shenandoah Valley. On July 9, a ragtag Union force under by Maj. Gen. Lew Wallace tried to halt Early along the Monocacy River, just east of Frederick. Wallace, who was joined by another division moved north from the Petersburg lines, was outflanked and beaten after a valiant fight. Early continued his march towards the Federal capital after beating Wallace. Wallace's defeat at Monocacy gave time for more reinforcements to boost Washington's defenses.