Oliver Otis Howard, Autobiography of Oliver Otis Howard, major general , United States army : volume 1

Heintzelman,when he had crossed the river with his corps, had moved Hooker's division to the neighborhood of White Oak Swamp Bridge, three miles due south of Bottom's Bridge, and Kearny's division forward on the Richmond road about half as far, stopping it a little short of Savage Railway Station. Heintzelman in his own corps had for duty at the first symptoms of battle about 20,000 men. He was the ranking officer and in command of all the troops south of the Chickahominy. The Eighth Pennsylvania and part of the Eighth Illinois Cavalry were present to watch the flanks of Couch and Casey, but not able to do much in such a thickly wooded region. Casey evidently felt the weakness of his force, for when the Confederate reconnoissance occurred on the 30th he sent at once to Keyes for help. Peck's brigade was placed on his left during that alarm.

Now came during that night a most terrific storm; the rain fell in torrents and it was accompanied by high winds. It was difficult to keep our tents standing and in that peculiarly soft soil the mud deepened and the discomforts were beyond description, so that the soldiers in every camp had little rest while the storm continued. The arms and ammunition were not improved by the pouring rain, though in these respects one side suffered no more than the other. But for some reason those who stand on the defensive are more subject to discouragement and apprehension than those who are in movement.

General Johnston, the Confederate commander, had a few days before planned a combined attack