R. Lee Ermey enlisted in the Marine Corps in 1961. He served as a drill instructor at Marine Corps Recruit Depot in San Diego from 1965 to 1967.
Along with serving as a drill instructor, Ermey was also a rifleman and repair shop mechanic throughout his time in the Corps.
In 1968, he arrived in Vietnam where he served 14 months attached to Marine Wing Support Group 17. He then served in Okinawa and he rose to the rank of Staff Sergeant.
In 1972 he was medically discharged for various injuries sustained during his service.
On May 17, 2002 Ermey received an honorary promotion to Gunnery Sergeant, thus becoming the first retiree in the history of the Marine Corps to be promoted.