In 1961, at age 17, Ermey enlisted in the United States Marine Corps and went through recruit training at Marine Corps Recruit Depot San Diego in San Diego, California.[2] For his first few years, he served in the aviation support field before becoming a drill instructor in India Company, 3rd Recruit Training Battalion, at Marine Corps Recruit Depot San Diego, where he was assigned from 1965 to 1967.[4]
Ermey then served in Marine Wing Support Group 17 at Marine Corps Air Station Futenma in Okinawa, Japan.[2] In 1968, he was ordered to Vietnam with MWSG-17, and spent 14 months in country. The remainder of his service was on Okinawa where he was advanced to staff sergeant (E-6). He was medically discharged in 1972 because of several injuries incurred during his service.[5] On May 17, 2002, he received an honorary promotion to gunnery sergeant (E-7) by the Commandant of the Marine Corps, General James L. Jones.[6]