James Ford Rhodes (18481927). History of the Civil War, 18611865 1917.
McClellan had three corps on the north side of the Chickahominy river and two on the side toward Richmond, and that the purposed reënforcement of the Army of the Potomac by McDowell had been abandoned. He therefore resolved to strike on May 31 at the two corps nearest to Richmond. On the night of the 30th, there was a heavy rain turning the treacherous and already high Chickahominy into a torrent and increasing the danger of the divided Union Army and the eagerness of Johnston to give battle, despite the roads deep with mud and the consequent difficulty of moving his artillery. At some time after midday, he attacked the two corps with vigor, drove them back and came near inflicting on them a crushing defeat [Battle of Fair Oaks or Seven Pines]. But General Sumner saved the day. Receiving the order from McClellan to be ready to move at a moments notice but, comprehending the danger better than his chief and construing the order freely, he at once marched his two divisions to his two bridges, halted and anxiously awaited further commands. Word at last came to cross the river. Sumners corps went over the swaying and tossing bridges and preserved the Union left wing from rout. The Southern Army suffered a grievous loss in the severe wounding of General Johnston, who was knocked from his horse by the fragment of a shell near the end of the fight, and borne unconscious from the field.
On the next day the battle was renewed. The Confederates were driven back and some of the Union troops pushed forward to within four miles of Richmond. These were from the left wing; receiving no orders to advance farther, they fell back to the lines they had occupied before the battle. The action of the two days may be summed up as a partial success of Johnston and in the end a repulse of the Confederates.1