the HHC, and to support the battalion primary staff by facilitating the environment in which they operate and in turn support the battalion commander in commanding the battalion. While the Headquarters Company Commander has administrative authority over the battalion commander's staff officers and NCOs, the Headquarters Company Commander's operational authority is limited to requirements derived from exercising the HHC's mission essential task list (METL) through related collective training requirements that facilitate the battalion commander's command post, in addition to achieving required individual training: "...ensuring that both Soldiers and equipment are in the proper state of readiness at all times". At the brigade and division level, an HHC is similarly constituted of the brigade commander or division commander, his or her staff, and the support elements, but the ranks of the staff and support personnel are typically greater to reflect the greater level of responsibility at higher echelon units. However, the company commander of a brigade or division Headquarters Company is usually still a captain. In keeping with the army's long-standing practice of referring to company-sized artillery units as "batteries" and company-sized cavalry units as "troops," the headquarters company element of an artillery battalion or higher is referred to as a headquarters and headquarters battery, or HHB, and the headquarters company element of a cavalry squadron or higher is referred to as a headquarters and headquarters troop, or HHT. Additionally, some high-level headquarters elements for special units are not company-sized and are referred to as "detachments"; as a result, these units are formally referred to as headquarters and headquarters detachments, or HHD. See also Units, formations, and commands Staff officer Headquarters and Service Company References Military units and formations by type Companies of the United States Army