UNSC Army

The UNSC Army is the primary surface warfare branch of the United Nations Space Command. The Army is mainly a defensive garrison force used to occupy human colonies in the long term, contrasted with the expeditionary nature of the UNSC Marine Corps. As their defensive roles are similar, the Army is closely associated with the UNSC Aerospace Force and the two share many of their facilities. Most Army assets fall under UNICOM.

In keeping with its localized nature, the Army's culture is less universally defined than that of the Navy or Marine Corps, with many planetary garrisons having their own customs and traditions, coupled with a selection of equipment suited to the local environment. The Army is also far numerically larger and fields a wider array of assets than the Marine Corps. This includes not only ground warfare assets but also most of the UNSC's maritime craft such as aircraft carriers, submarines, and mobile launch platforms. Although sometimes called the "wet navy", the Army's Maritime Operations is a completely separate organization from the Navy that developed largely on its own.

Although they are primarily a garrison force, Army forces may also be deployed in long-term expeditionary campaigns; this occurred several time during the the Inner Colony Wars and Insurrection. However, such deployments were rare during the Human-Covenant War due to the rapid pace of the fighting; in most cases, a colony would fall before the UNSC could mobilize a massed response. On interstellar deployments, Army forces mainly rely on the UNSC Navy for transportation.

While they are a permanent fixture in SolCore and most Inner Colonies, Army garrisons are not universal throughout human space. Some colonies maintain their own defensive forces or militias, which acts as a resource-saving measure for the UNSC. This became increasingly prevalent during and after the Human-Covenant War and into the Phoenix Initiative as the UNSC looked into shifting its doctrine toward ever greater mobility. Colonies were encouraged to develop their own defense forces to remove pressure from the UNSC, though the Army continued to operate on worlds strategically important to the UNSC. On some worlds, preexisting Army garrisons were effectively converted into defense forces under the colonial government, rather than being directly tied to the UNSC.