The aggressive Maj. Gen. Philip Sheridan, a key subordinate of Lt. Gen. Ulysses S. Grant, was dissatisfied with Warren's performance. He was angry at Warren's corps for supposedly obstructing roads after the Battle of the Wilderness and its cautious actions during the Siege of Petersburg. At the beginning of the Appomattox Campaign, Sheridan requested that the VI Corps be assigned to his pursuit of Lee's army, but Grant insisted that the V Corps was better positioned. He gave Sheridan written permission to relieve Warren if he felt it was justified "for the good of the service." Grant later wrote in his "Personal Memoirs",