In the early hours of June 27, 1862, the third of the Seven Days' battles, Fitz John Porter’s Union corps abandoned its position at Beaver Dam Creek and established a new defensive line behind Boatswain’s Swamp, just north of the Chickahominy River. Anxious to renew his assaults from the day before, Confederate General Robert E. Lee, sent the bulk of his force forward with the intention of driving them across the river. The Federals beat back successive waves of disjointed attacks, inflicting some of the heaviest casualties the war had yet seen. By dusk, however, Lee’s Confederates were more organized. With daylight fading, the reinforced Southerners assaulted Porter’s anemic defensive line and sent the Northerners fleeing toward the river. Only darkness prevented Porter’s corps from complete disaster. During the night, the Federals limped across the Chickahominy and burned the bridges behind them.