This was the third of the Seven Days' Battles.
On June 27, 1862, CSA General Robert E. Lee renewed his attacks against USA Brigadier General Porter's V Corps, which had established a strong defensive line behind Boatswain's Swamp north of the Chickahominy River.
Porter's reinforced V Corps held fast for the afternoon against disjointed Confederate attacks, inflicting heavy casualties.
At dusk, the Confederates finally mounted a coordinated assault that broke Porter's line and drove his soldiers back toward the river.
The Federals retreated across the river during the night.
Defeat at Gaines' Mill convinced Union General McClellan to abandon his advance on Richmond, Virginia and begin the retreat to the James River. Gaines' Mill saved Richmond for the Confederacy in 1862.
Result(s): Confederate victory
Location: Hanover County
Campaign: Peninsular Campaign (March-September 1862) next battle in campaign previous battle in campaign
Date(s): June 27, 1862
Principal Commanders: Brigadier General Fitz John Porter [US]; General Robert E. Lee [CS]
Forces Engaged: 91,232 total (US 34,214; CS 57,018)
Estimated Casualties: 15,500 total (US 6,800; CS 8,700)
Seven Days Battles Map