[1][2] After graduating from The Citadel in 1963, where he received a degree in English, Hartzog was commissioned in the Infantry.

He deployed to South Vietnam in 1967, eventually commanding a company, and upon return to the United States he attended the Infantry Officer Advanced Course.

Hartzog attended the United States Marine Corps Command and Staff College from 1973 to 1974, then proceeded to Fort Riley, Kansas where he served in various staff positions with the 1st Infantry Division.

Following promotion to brigadier general, Hartzog served from 1987 to 1989 as the Assistant Commandant of the United States Army Infantry School, then returned to Panama for a third time as the J-3, United States Southern Command, a position he held during Operation Just Cause.

After retiring from the army, Hartzog became CEO of Burdeshaw Associates, a defense consulting firm,[3] sat on the board of directors of the Army Historical Foundation,[4] and was a member of the Defense Science Board.