The Joint Staff (JS) is a military headquarters staff based at the Pentagon, (with offices in Hampton Roads, Virginia, Fort Leavenworth, Kansas, Lackland Air Force Base, Texas, Fort Belvoir, Virginia, Fairchild Air Force Base, Washington and Fort McNair, District of Columbia) composed of personnel from all the five armed services, assisting the chairman and the vice chairman in discharging their responsibilities. They work closely with the Office of the Secretary of Defense (OSD), the military department staffs, and the Combatant Command staffs.