The operational chain of command runs from the President to the Secretary of Defense to the combatant commanders of the combatant commands. The Chairman of the Joint Chiefs of Staff may transmit communications to the Commanders of the combatant commands from the President and Secretary of Defense and advises both on potential courses of action, but the Chairman does not exercise military command over any combatant forces. Under Goldwater–Nichols, the service chiefs (also four stars in rank) are charged with the responsibility of the "strategic direction, unified operation of combatant commands, and the integration of all land, naval, and air forces in an efficient "unified combatant command" force. Furthermore, the Secretaries of the Military Departments (i.e. Secretary of the Army, Secretary of the Navy, and the Secretary of the Air Force) are legally responsible to "organize, train and equip" combatant forces and, as directed by the Secretary of Defense, assign their forces for use by the combatant commands. The Secretaries of the Military Departments thus exercise administrative control (ADCON) rather than operational control (OPCON—the prerogative of the combatant commander) over their forces.