With the Confederate defeat at Five Forks on April 1st, Lieut. Gen. Ulysses S. Grant and Maj. Gen. George Meade ordered a general assault against the Petersburg lines by the Second, Ninth, Sixth and Twenty-Fourth Corps to take place April 2nd. In the pre-dawn darkness, the Union infantry gained a successful breakthrough where Maj. Gen. Horatio G. Wright's advancing Sixth Corps met the Confederate lines held by Maj. Gen. A. P. Hill near the Boydton Plank Road. Hill was killed trying to reach his troops in the confusion. A heroic defense of Fort Gregg by about 600 Confederates against nearly 5,000 Federals prevented Union forces from entering the city that evening. Wright's breakthrough and the subsequent follow-up troops surged north and severed the South Side Railroad near Petersburg. The Union Army now had access to the Appomattox River and were free to cross the next day to threaten Lee’s communications on the north side of the river. After dark, Lee informed President Jefferson Davis that he could "hold his position no longer," and that Petersburg and Richmond must be evacuated. Grant had finally achieved one of the major military objectives of the war: the capture of Petersburg, which led directly to the loss of the Confederate capital at Richmond, which finally fell on April 3rd.