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Chapter 2 2-20 ADP 3-90 31 July 2019 2-99. Groups are brigade-size organizations that, because of Army modularity, are rarely used outside of Army’s special operations forces. Army special operations forces use the term to designate large special forces and psychological operations units. The Army’s modular design deactivated group headquarters in favor of activating additional brigade headquarters. Explosive ordnance disposal, criminal investigation division, regional support groups, specialized aviation units, and specialized intelligence units are exceptions to this rule. DIVISIONS 2-100. A division is an echelon of command and tactical formation that employs brigade combat teams, multi-functional brigades, and functional brigades to achieve objectives on land. It is normally employed as a tactical headquarters that employs a combination of BCTs, multifunctional brigades, and functional brigades to operate as a formation. Two to five BCTs, a sustainment brigade, a combat aviation brigade, a division artillery headquarters and headquarters battery, and a maneuver enhancement brigade are assigned to a division conducting large-scale ground combat operations. A division headquarters is a self-contained organization with a command group and a fully functional staff that requires no staff support from subordinate units to provide capabilities for its primary role. The Army organizes each division headquarters staff into a division headquarters and headquarters battalion. That battalion is augmented by a reserve component main command post operational detachment to provide it with additional capacity. Functional support brigades consist of military police, engineer, air and missile defense, and military intelligence brigades. Functional support brigades normally have command relationships with a division headquarters (assigned, attached, operational control, or tactical control). 2-101. A division headquarters provides a flexible command and control capability in all operational environments. A division headquarters may be used in other roles, including acting as the senior Army headquarters, joint force land component, or a joint task force headquarters in a joint operations area for small-scale operations. However, when performing these roles, a division requires significant Army and joint augmentation. 2-102. The mission variables determine the optimal size and mix of capabilities of the forces task-organized under each division headquarters. The size, composition, and capabilities of the forces task-organized under a division headquarters may vary between divisions involved in the same joint campaign and may change from one phase of that campaign to another. Operations focused on the destruction of a conventional enemy may require a mix of forces and capabilities that differ from those required for an operation focused on protection of civil populations. 2-103. A division normally operates as a tactical headquarters under the operational control of an Army corps, ARFOR, or joint force land component commander. The ARFOR is the Army component and senior Army headquarters of all Army forces assigned or attached to a combatant command, subordinate joint force command, joint functional command, or multinational command (FM 3-94). As a tactical echelon, a division headquarters arranges multiple tactical actions of its subordinates in time, space, and purpose to achieve significant military objectives. A division headquarters leverages joint force capabilities and conducts shaping operations within its AO to create favorable conditions for the success of its subordinate units. A division headquarters allocates resources, designates the main and supporting efforts, forecasts operational requirements, and establishes the priorities of support within its task-organized forces. Sustainment, medical, and functional units (including military police, engineer, air and missile defense, and military intelligence) in command or support relationships with a division operate in accordance with established priorities. CORPS 2-104. A corps is an echelon of command and tactical formation that employs divisions, multi-functional brigades, and functional brigades to achieve objectives on land. Large-scale combat operations may require a corps headquarters to function as a tactical land headquarters under an operational-level command, such as a joint or multinational land component command. A corps headquarters is organized, trained, and equipped to control the operations of two to five divisions, together with supporting theater-level organizations. The distinguishing differences between corps and division operations are their scope and scale. During large- scale combat operations, a corps conducting tactical operations operates as a large combined arms formation employing capabilities within and across multiple domains, not just as a headquarters. Normally, a corps