From Halopedia, the Halo wiki
Lieutenant, abbreviated to LT, is a junior commissioned officer rank of O-3 in the United Nations Space Command Naval Command (NAVCOM) rank structure; including the UNSC Navy and Office of Naval Intelligence. It is preceded by Lieutenant Junior Grade, and subordinate to a Lieutenant Commander.[1]
Command of work division or captain of support ship.[1]
Lieutenant - Halo 5: Guardians (Angle 1)
Enlisted: Crewman Recruit • Crewman Apprentice • Crewman • Petty Officer Third Class • Petty Officer Second Class • Petty Officer First Class • Chief Petty Officer • Senior Chief Petty Officer • Master Chief Petty Officer
Enlisted: Private • Private First Class • Lance Corporal • Corporal • Sergeant • Staff Sergeant • Gunnery Sergeant • Master Sergeant • First Sergeant • Master Gunnery Sergeant • Sergeant Major