Despite his victory over the Confederates at Beaver Dam Creek on June 26th, Maj. Gen. Fitz John Porter’s Fifth Corps abandoned its position early on June 27th and established a new defensive line along Boatswain’s Creek, just north of the Chickahominy River. Porter's orders from Maj. Gen. George B. McClellan were to hold off Robert E. Lee's army long enough for McClellan to begin moving the Army of the Potomac south towards the James River. Porter, with around 34,000 men, was outnumbered by Lee's nearly 60,000 men with his back to the Chickahominy.  The clear, high ground south of Boatswain's Creek around the Watt family farm gave Porter good clear ground to place artillery, and his infantry used the banks of the creek to their advantage. Anxious to renew his assaults from the day before, Lee sent the bulk of his force forward late on the 27th with the intention of driving Porter's men 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 entire defensive line and sent the Northerners fleeing toward the Chickahominy.  Only darkness saved Porter’s corps from complete disaster.  During the night, the Federals limped across the river and burned the bridges behind them.  Gaines' Mill was the third in the Seven Days battles and began a series of rearguard actions as McClellan moved his army to the James River.