Brig. Gen. Fitz John Porter, USA
The Confederates attacked with over 16,000 men, while the Union had about 15,500.
The Confederates suffered about 1,300 casualties, the Union 400.
This is the second of the Seven Days' Battles, in which Lee opened his offensive against McClellan's right flank north of the Chickahominy River. The plan was for AP Hill to pin Fitz John Porter's front while Stonewall Jackson swung around the Union rear. But confusion reined. Jackson was late, and as the day slipped away it looked like surprise was going to be lost. AP Hill went ahead and attacked with his division, reinforced by one of D.H. Hill's brigades.
The attack was across a wide, marshy creek and the Union troops slaughtered the attackers, who kept coming in a series of futile assaults. Finally Jackson's Shenandoah veterans appeared, and McClellan's cautious nature asserted itself. Convinced he was outnumbered 2:1 he ordered Porter to fall back behind Boatswain Creek just beyond Gaines' Mill.