R. Lee Ermey is Gunnery Sergeant Hartman: the stereotypical Parris Island drill instructor who trains his recruits to transform them into Marines. In The Short-Timers, the character is named "Gerheim" and potbellied; he is a Second World War veteran of the Battle of Iwo Jima.
He is ruthless in his training towards his recruits, especially Leonard "Gomer Pyle" Lawrence, who he constantly attacks verbally. This makes Lawrence a Marine, but also turns him psychotic.
It results in his death at Pyle's hands.