Welcome to the Fourth Estate in U.S. Department of Defense

The "Fourth Estate" (also called the "4th Estate") is a jargon term used in the context of the U.S. Department of Defense (DoD). It refers to the non-military service portions of the DoD. The term generally encompasses defense agencies, DoD field activities, and certain other organizations (such as elements of the Office of the Secretary of Defense). These entities provide enterprise-wide support functions, including logistics, acquisition, finance, health, intelligence, personnel, and more. They are distinct from the military departments (Army, Navy, including the Marine Corps, Air Force, and Space Force) and the combatant commands. Some intelligence agencies (for example, the NSA, NGA, DIA, and NRO) are sometimes grouped under broader DoD structures. However, they are often distinguished as part of the Intelligence Community (IC) in official definitions. The exact composition can evolve slightly over time due to reorganizations. Typically, the Fourth Estate includes around 19 to 20 defense agencies and 8 field activities (totaling approximately 28 entities). These organizations employ tens of thousands of civilians and supporting contractors.