Headquarters and Service Company A Headquarters and Service Company is a company sized military unit , found at the battalion level and higher in the United States Marine Corps . In identifying a specific headquarters unit , it is usually referred to by its abbreviation as H & S . While a line company is formed of three or four platoon s , H & S is made up of the headquarters staff and headquarters support personnel of a battalion , MEU , regiment , MEB , division , or MEF . As these personnel do not fall inside one of the line companies of the battalion , regiment , or division , the H & S Unit is the unit to which they are administratively assigned . The typical personnel strength of an average H & S Company for a Marine infantry battalion is 270 personnel . Inside a battalion H & S , the headquarters staff will usually include the following key officers and primary staff officers : Depending on the unit , extra support officers will round out the staff , including one or two Navy Medical officer ( s ) , Career Planner , Judge Advocate , and a Navy Chaplain ( often collectively referred to as the " special staff " ) , as well as essential Navy and Marine Corps non - commissioned officer s and enlisted support personnel in the occupational specialities of the executive staff sections ( S1 through S4 and the S6 ) , and a battalion sergeant major , who is principal advisor to the battalion commander on matters regarding enlisted personnel . Additionally , H & S will contain further personnel assigned to support and sustain the mission of the battalion headquarters , including maintenance and motor transport , field mess , and supply . H & S itself will be commanded by a company commander ( usually a captain ) who is supported by a company executive officer ( usually a first lieutenant ) and a company first sergeant . All personnel in H & S fall under the administrative command of the H & S company commander , but in practice , the primary and special staff officers report directly to the battalion commander , and while the battalion commander is administratively assigned to H & S , he or she is the H & S company commander ' s higher commander and thus the H & S company commander operationally answers directly to the battalion commander . The mission of the H & S company commander is to run the administrative and Marine training aspects of H & S , 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 . At the regimental and division level , H & S is similarly constituted of the regimental 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 regimental H & S is usually still a captain . A division H & S is usually a battalion in itself and is commanded by a lieutenant colonel . In keeping with the long standing practice of referring to company sized artillery units as " batteries " the headquarters company element of an artillery battalion or higher is referred as a Headquarters and Service Battery . 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 Service Detachments .