UNSC Army

The UNSC Army is a branch of the UNSC Defense Force primarily responsible for land-based military operations.

Background
Little is known about the UNSC Army, which is probably due to the fact that the Army is almost exclusively a land-based fighting force, and thus little of the Army is attached to the UNSC Navy. What is known is that the UNSC Army uses different equipment from the UNSC Marine Corps, examples of such being the M6J Carbine, the MA37 Individual Combat Weapon System, and the M392 Designated Marksman Rifle, in contrast to the MA5B/MA5C assault rifles and BR55 Battle Rifle in use with the Marines. Soldiers of the UNSC Army wear the UNSC Army Battle Dress Uniform.

The UNSC Army maintains Airborne special forces units, equipped with the Air Assault helmet originally intended for Marine ODST issue. Army Pathfinder units prefer the FC-I variant of the AA helmet.

Role
It is known that the UNSC Army frequently patrols colony planets, but little is known about any operations they have participated in. Known operations include the Battle of Reach, where Army units assisted SPARTAN Noble Team in defending the planet, the Battle of Earth, where an Army unit tried to aid Marine forces in New Mombasa and was annihilated in the attempt, and the Battle of Mare Erythraeum on Mars, where Colonel James Ackerson led an unknown number of Army forces against the Jiralhanae commander Lepidus and his army. Unlike the Marines, who take offensive action against the enemy, the UNSC Army is largely used in defensive operations, such as garrisoning UNSC-held territory.

The UNSC Army supposedly also takes a large role in training colonial militia. While Marines have been known to train colonial militia, such as that of Harvest, it is far more likely that the Army, as the defensive arm of the UNSC, would normally take charge of maintaining militia forces.

It is also unknown what role the Army played in Operation: TREBUCHET and what actions they were apart of, although it is likely that TREBUCHET may have been a Marine exclusive counter-terrorism operation.

Trivia

 * The helmets worn by Army soldiers appear to be similar to those worn by the Marines, and may be the base of the MJOLNIR Military Police armor permutation in Halo: Reach's Armory. Additionally, their shoulder pauldrons are identical to the GUNGNIR shoulder pieces.
 * The UNSC Army makes its in-game debut in Halo: Reach, in which UNSC Army troopers, Marines, and ODSTs have their own service tags showing their name and rank as part of the Fireteam gameplay mechanic. Most of them are named after Bungie and Rooster Teeth employees.