GRSC Army (Earth-2042)

The GRSC Army was a branch of the GRSC Armed Forces, and was primarily responsible for land-based military operations alongside the GRSC Marine Corps and other land-based forces. Unlike the Marine Corps, which was typically deployed in expeditionary operations across the galaxy in conjunction with the GRSC Navy, the Army was primarily implemented in ground combat operations and garrison duties, serving as a major part of the GRSC Defense Force alongside the GRSC Air Force.

Source

 * https://www.halopedia.org/UNSC_Army