Ranks

Crewman Recruit is the lowest enlisted rank of the UNSC Navy. Entry level for all new ONI accepted recruits and the lowest ranked personnel. They embody the main composition of ships. Must carry out orders and duties issued to them to the best of their ability.

Crewman Apprentice is the second enlisted rank of the UNSC Navy. It is based on the US Navy's rank of Seaman Apprentice and serves similar roles.

Crewman is the third enlisted rank of the UNSC Navy, It is the highest non-NCO enlisted rank in the Navy, directly below Petty Officer Third Class and directly above Crewman Apprentice. A crewmen that is leading in his/her class or deck in a specific area can also be called Crew Chief. 

Petty Officer Third Class is the fourth enlisted rank of the UNSC Navy and the lowest rank of non-commissioned officer, or NCO. In informal settings, a Petty Officer Third Class is typically called a "Petty Officer."

 Petty Officer Second Class is the fifth enlisted rank of the UNSC Navy and is a non-commissioned officer.

Petty Officer First Class is the sixth enlisted rank of the UNSC Navy and is a non-commissioned officer. There is no preferential treatment despite the rank name might suggest. Petty Officer First Class(s) are the final rank earned showing others achievement to the UNSC Navy.

Chief Petty Officer is the seventh enlisted rank of the UNSC Navy and is a senior non-commissioned officer. In informal settings, Chief Petty Officers are typically called "Chief." Not to be confused with Master Chief and the Master Chief Petty Officer rank.

Senior Chief Petty Officer is the eighth enlisted rank of the UNSC Navy and is a senior non-commissioned officer. In informal settings, Senior Chief Petty Officers are typically called "Senior." It is generally assumed that a Senior Chief Petty Officer is the eldest on the ship but not always true.

Master Chief Petty Officer is the ninth enlisted rank of the UNSC Navy, and is a senior non-commissioned officer. It is a rank enamored by many due to the stories played through the eyes of John 117 commonly referred in and out of the game as the Master Chief.