Gaines's Mill, Battle of, June 27, 1862, a Confederate victory in the American Civil War. This battle, part of the Seven Days' Battles of the Peninsular Campaign, is sometimes called the First Battle of Cold Harbor. It was fought eight miles (13 km) northeast of Richmond, Virginia. After stubborn resistance, the outnumbered Union troops (35,000, against 57,000 Confederates) retreated toward Harrison's Landing on the James River. The Union commander was General Fitz-John Porter. The main Confederate attacks were delivered by Generals James Longstreet and A. P. Hill.