Final answer:
The Combatant Command (CCMD) is the primary agency responsible for communicating command directions to operational organizations of the entire installation, functioning under the authority of the President and Secretary of Defense.
Step-by-step explanation:
The primary agency authorized to communicate command directions to operational organizations supporting the entire installation is the Combatant Command (CCMD). The Combatant Commands are established as the highest echelon of military structure, they are charged with providing command and control for all military forces in accordance with the chain of command established by the President, as Commander in Chief, and the Secretary of Defense. The CCMDs are responsible for a geographic or functional area and have broad, continuing missions that require them to command assigned forces from multiple Services, such as the Army, Navy, Marine Corps, Air Force, and Coast Guard which are all overseen by the President.