The rank structure of the United Nations Space Command's mainline branches of service (the Navy, the Marine Corps, the Army, and the Air Force) is largely derived from the system employed by the 21st century United States military.

Overview

The UNSC's rank structure is similar to that used by 21st century militaries, primarily the United States military. Unlike contemporary military forces, however, the UNSC largely employs two main rank schemes throughout its organisation; NAVCOM rankings for organisations within UNSC Naval Command (namely, the UNSC Navy and Office of Naval Intelligence) and UNICOM rankings for Unified Ground Command subordinates (UNSC Army, Air Force, Marine Corps). UNSC ranks can be broadly categorized into several groupings;

• Enlisted: Regular personnel who perform the "front line" duties. This includes regular infantry personnel.
• Non-commissioned Officers: Non-commissioned officers (NCOs) are enlisted personnel that fill most intermediary leadership and administrative roles. Their responsibilities vary by service, occupational specialty and duty station. The UNSC relies heavily on NCOs, and they share many responsibilities with officers.
• Warrant Officers: Warrant officers are technical specialists and subject matter experts who are given an officer's commission in recognition of their expertise and leadership role. They take the officer's oath of service and are rated above enlisted troops but are subordinate to full officers. The Air Force does not select or utilize warrant officers, and they are rarely found in the Marine Corps.
• Officers: UNSC officers are commissioned, meaning that their authority is granted by a formal legal document issued on the authority of the UEG President. This commission is awarded after the completion of Officer Candidate School (OCS) and after taking the oath of service.

NAVCOM ranks

UNSC Naval Command uses rank titles which are different to the other branches. Navy ranks and terminology have a long history which dates back to eras when ships sailed on the oceans of Earth rather than in space. These ranks are used by the UNSC Navy and ONI.

Enlisted ranks

Rank	Crewman Recruit (CR)	Crewman Apprentice (CA)	Crewman (CR)	Petty Officer Third Class (PO3)	Petty Officer Second Class (PO2)	Petty Officer First Class (PO1)	Chief Petty Officer (CPO)	Senior Chief Petty Officer (SCPO)	Master Chief Petty Officer (MCPO)
Typical responsibilities	Boot camp and training school	Initial fleet assignment	Work crew	Work party lead	Compartment supervisor	Work division supervisor	Deck supervisor	Oversight of ship enlisted personnel	Fleet administration or HIGHCOM staff

Officer ranks

Rank code

OT

WO-1

WO-2

O-1

O-2

O-3

O-4

O-5

O-6

O-7

O-8

O-9

O-10

Rank

Cadet (CDT)

Warrant Officer (WO)

Chief Warrant Officer (WO-2)

Ensign (ENS)

Lieutenant Junior Grade (LTJG)

Lieutenant (LT)

Lieutenant Commander (LCDR)

Commander (CDR)

Captain (CAPT)

Rear Admiral (RADM)

Vice Admiral (VADM)

Admiral (ADM)

Fleet Admiral (FADM)

Typical responsibilities

No command authority

Resident technical expert

Command advisor or captain of utility ship

Initial officer posting

Command of staff section

Command of work division or Captain of support ship

First officer on small warship or command of ship department

HIGHCOM staff or captain of small warship

Captain of line warship or installation

Battle group commander

Command of Sector fleet or academy

HIGHCOM staff

Fleet commander

UNICOM ranks

UNSC ground forces rely on little administrative overheard and bureaucracy thanks to artificial intelligences and automated services, which handle the majority of routine paperwork and coordination. The UNSC's standards of training and high "tooth to tail" ratio of fighting troops to support personnel also allow senior enlisted and junior officers to be given much more responsibility and command authority that what was historically possible. Some UNSC Army and Air Force personnel additionally make use of ranks and/ or roles that do not fit into the UNICOM system of organisation.

Enlisted ranks

Rank code	E-1	E-2	E-3	E-4	E-5	E-6	E-7	E-8	E-9
Rank	Private (PVT)	Private First Class (PFC)	Lance Corporal (LCPL)	Corporal (CPL)	Sergeant (SGT)	Staff Sergeant (SSGT)	Gunnery Sergeant (GYSGT)	Master Sergeant (MSGT) First Sergeant (1SGT)	Master Gunnery Sergeant (MGSGT) Sergeant Major (SGTMAJ)
Typical responsibilities	Boot camp and training school	Initial assignment	Fireteam assistant	Fireteam leader	Squad leader	Assistant platoon leader	Assistant company commander	Division administration, E-8 technical career track Assistant battalion commander, E-8 command career track	Staff lead, E-9 technical career track Assistant division commander, E-9 command career track

Officer ranks

Rank code

OT

WO-1

WO-2

O-1

O-2

O-3

O-4

O-5

O-6

O-7

O-8

O-9

O-10

Rank

Cadet (CDT)

Warrant Officer (WO)

Chief Warrant Officer (WO-2)

Second Lieutenant (2LT)

First Lieutenant (1LT)

Captain (CPT)

Major (MAJ)

Lieutenant Colonel (LTCOL)

Colonel (COL)

Brigadier General (BGEN)

Major General (MGEN)

Lieutenant General (LTGEN)

General (GEN)

Typical responsibilities

No command authority

Crew chief or Army pilot

Senior subject matter expert

Platoon commander

Company executive officer

Company commander

Battalion executive officer

Battalion commander

Brigade commander

Division commander

Task Force commander

CENTCOM commander

HIGHCOM senior staff

Spartan Operations

Unlike NAVCOM and UNICOM, the Spartan Operations branch does not employ traditional ranks. Instead, the Spartan branch works to take the informal leadership traditions of the SPARTAN-IIs and adapt them into a structure than emphasizes independence and unity of purpose over rigid adherence to the chain of command. Nevertheless, SPARTAN-IV personnel are given additional responsibilities and authority as they advance in their careers. All Spartans receive a direct commission as an officer of the UNSC, though this authority does not typically extend out of their chain of command.

While aboard naval vessels, Spartans report directly to the ship's captain in all matters relating to the safety and security on-board the ship - superseding all other responsibilities and orders. In all other cases, the Spartan Commander has operational control of Spartan personnel, and Spartans cannot give or be given orders to/ from Navy or ONI personnel. Spartans are, however, encouraged to accommodate reasonable respects where they do note violate existing orders or the Spartan Code.

Spartan ranks

Role	Spartan	Fireteam Leader	Mission Handler	Spartan Commander	Director of Spartan Operations
Responsibilities	Augmented special forces equipped with MJOLNIR Powered Assault Armor.	Field leader of a fireteam of 4-5 Spartans.	Spartan Command liaison and intelligence support stationed at headquarters. Responsible for managing 5-10 fireteams, or 20-50 Spartans.	Overall command-and-control of Spartan Company. Responsible for upwards of 300 Spartans.	Commander-in-Chief of the Spartans (CINCSPAR)
UNSC authority	First Lieutenant	Captain	Major	Colonel	General

Trivia

• The Halo Encyclopedia erroneously describes the structure and insignia of the UNSC's ranking system as being identical to those used in Halo multiplayer, Halo 3 in the original printing and Halo: Reach in the 2011 edition.
• All Marine Corps ranks between Staff Sergeant and Sergeant Major are classified as Staff non-commissioned officers.