The 76th Ohio was part of the Army of the Tennessee. Humphrey rose quickly through the ranks and was promoted to first lieutenant. He participated in twenty-seven battles and skirmishes including Fort Donelson, Shiloh, Corinth, the siege of Vicksburg, Resaca, and Atlanta. The regiment participated in the march to the sea and through the Carolinas to the battle of Bentonville. At Ringgold Gap on November 27, 1863, Humphrey was wounded but missed no duty due to the wound. He was mustered out with the regiment at Louisville, Kentucky on July 19, 1865.