Northern Name for Battle: Gaines' Mill Southern Name for Battle: Gaines' Mill Location of Battle: Washington County, Maryland Date of Battle: June 27, 1862 Northern Commander: F.J. Porter Southern Commander: Robert E. Lee Winner: Confederate Northern Troops Involved: 34,214 Southern Troops Involved: 57018 Northern Casualties: 6,800 Southern Casualties: 1,560 Interesting Facts: Several of McClellan's subordinates urged him to attack John Magruder's division, but he didn't becaused he believed there was far more confederates than there really was.