Enlisted as a Private in Macon, Georgia, on June 13, 1862 for the war with Company I, "Carswell Guards," Third Georgia Volunteer Infantry Regiment. He joined this unit at Drewry's Bluff, Virginia, on August 1, 1862. He was last paid with his unit on April 30, 1863, and was hospitalized during May and June, 1863 at the Huguenot Springs Military Hospital near Richmond, Virginia. Marcus was transferred to a hospital in Toomsboro, Georgia in July 1863. He was furloughed and died at home in Laurens County, Georgia on August 15, 1863.
The above is interpreted from his service records and the applications his widow, Rachel [Skipper] Bellflower filed after his death.