UNSC military organization

The Organization of the UNSC Military is the way in which the UNSC Navy and UNSC Marine Corps organize their fighting forces into manageable sizes of manpower for use in combat operations. Though there have been many UNSC military units named in the books and games, the exact specifications of the UNSC armed forces organization remains unclear. For a complete list of all known UNSC Military units, see List of UNSC Military Units.

UNSC Marine Corps
The large-unit structure of the UNSC Marine Corps appears to mirror the organizational structure of the United States Marine Corps in most distinguishable ways, however the small-unit structure is more unique and in some ways still unclear. A nearly complete chart showing the sourced known structure of the UNSC Marine Corps units can be seen below. Current Halo canon focuses heavily on small unit interactions, with units at any strength higher than a Battalion being only occasionally mentioned and never elaborated upon. This has caused a lack of information regarding the specifics of larger UNSC Marine commands. Small units structure is often referenced indirectly. The below chart shows unit strength and specifics that can be applied to all (as of yet ) known units.

Exceptions
The above system seems to fit most stated units of the UNSC armed forces, but not all unit designations are clear. Specifically, the use of unit abbreviation codes make it particularly difficult to properly identify units. An example of this is the unit 3/1 Bravo, seen in Halo: Combat Part 2. "3/1 Bravo" could possibly stand for "Bravo Company, 1st Battalion, 3rd Marine Regiment", however, "Fireteam Bravo, First Squad, Third Platoon" is just as reasonable a translation of the code. More complicated codes arose in Halo 3, such as S4/BAG/2/5 and E2-BAG/1/7, which have even more variables.

The only time a unit abbreviation code is translated is page 111 of Halo: Contact Harvest, where M-EDF 9/21/1 is translated as 9th Marine Expeditionary Force, 21st Marine Division, 1st Battalion. This adds further mystery to the scheme, as it apparently skips over the Regimental command and implies that the Battalion is directly subordinate to the Division level headquarters, a fact that no other source has ever stated and does not make sense according to standard military organization.

Unit designations are also deeply convoluted, due to the great use of acronyms which are not used in modern militaries and have not yet been directly spelled out. References have been made to "BAG" units (as seen above) where no modern military designates any type of combat unit with the acronym "BAG", and the many possible meanings of the acronym make it unclear what a "BAG" unit is. Other anomalies include 2BN/3U, where "2BN" is short for 2nd Battalion, but what "3U" stands for is unclear, and only assumed to be "Third Unit." The mentioned Twenty-Second Tactical, (having received no further designation, and could be of virtually any size) and the 105th Drop Jet Platoon (going against the established scheme of not providing permanent designations for Platoons) are even further examples of the confusion caused by clashing sources of information.

UNSC Navy
The UNSC Navy command structure has received even less attention than the UNSC Marine Corps. Mentions have been made of Battle Groups containing less than ten vessels being used, but it is unclear if battle groups are permanent assignments for ships or not. Additionally, numbered fleets have been mentioned, but no information about them other than their number designation has been revealed, making it impossible to infer what the UNSC Fleet organization is.