The Battle of Gaines' Mills, also known as the Battle of Chickahominy was an engagement of the American Civil War that took place on June the 27th, 1862. Porter, commanding 20,000 troops of McClellan's army, was defeated by Robert E Lee with a Confederate force of 35,000. On. the morning of June the 27th, Porter fell back to a range of low hills, and there repelled the Confederate attack until 5000 more men were sent him by McClellan. Meantime Jackson had joined Robert E Lee with 25,000 fresh troops. A P Hill first attacked Porter's position, and was driven back with great loss after a two hours' struggle. Then Jackson came up and joined the attack. Porter, having no entrenchments, was forced to give way before the superior numbers. He crossed the Chickahominy in rapid retreat, and burned the bridges behind him. Research Battle of Gaines' Mills