Adam Badeau, Military history of Ulysses S. Grant from April 1861 to April 1865. Volume 2

While Warren was thus elaborately, and, as it seemed to his superior, too slowly, taking position, Sheridan learned that the left of the Second corps of the army of the Potomac had been swung around till it fronted on the Boydton road. This created an opportunity for the enemy to march down from the White Oak road and attack the right or rear of Sheridan's new position. Mackenzie was therefore sent up by the Crump road across Warren's rear, with directions to gain the White Oak road if possible, and attack any enemy he found, at every hazard. He would thus protect the rear of Warren against any intervention of the enemy from that direction. If successful in this, Mackenzie was to march back by the White Oak road and rejoin Sheridan, coming in on the right of the infantry. He executed his orders with skill and courage, attacking a force of the enemy on the White Oak road, and driving it back towards Petersburg. Then countermarching, he rode up to Sheridan, just as the Fifth corps was advancing to the attack. Sheridan directed him to swing around to the right of the infantry, and gain possession of the Ford road at the crossing of Hatcher's run, and thus cut off the rebel line of retreat towards Lee.

It was five o'clock before the Fifth corps was ready, but at that hour the battle began. The object of the assault was the angle in the rebel fortified line; this was to be destroyed before the troops that held it could be reinforced, while the cavalry