Keith was born on June 18, 1925, in Sturgis, Michigan, and enlisted in the Army Air Corps, graduating in 1943.
Assigned to the 465th Bomb Group of the 15th Air Force, he flew as a bombardier and top turret gunner aboard a B-24 Liberator out of Pantanella Airfield, Italy, striking targets across Romania, Germany, Austria, Hungary, and the Balkans. On his very first mission, mechanical trouble forced the crew to bail out near Bucharest, where they spent three weeks in the care of Soviet forces before being flown back to their base. On his fifth mission, flak knocked the plane out of the sky; the entire crew bailed out successfully and was recovered within British lines. He went on to fly 28 more missions. Between combat, Keith found another outlet: an accomplished trumpet player, he performed in a band that flew aboard a dedicated B-24 to entertain Allied troops throughout the theater.
He was honorably discharged in October 1945.