Department of Defense
DIRECTIVE
NUMBER 5100.01
December 21, 2010
Incorporating Change 1, September 17, 2020
CMO
SUBJECT: Functions of the Department of Defense and Its Major Components
References: See Enclosure 1
1. PURPOSE. This Directive:
a. Reissues DoD Directive (DoDD) 5100.1 (Reference (a)).
b. Establishes the functions of the Department of Defense and its major Components,
supporting the core mission areas of the Armed Forces, which are broad DoD military operations
and activities required to achieve the strategic objectives of the National Security Strategy,
National Defense Strategy, and National Military Strategy (References (b), (c), and (d)), in
accordance with title 10, United States Code (U.S.C.) (Reference (e)).
2. APPLICABILITY. This Directive applies to OSD, the Military Departments, the Office of
the Chairman of the Joint Chiefs of Staff and the Joint Staff, the Combatant Commands, the
Office of the Inspector General of the Department of Defense (IG DoD), the Defense Agencies,
the DoD Field Activities, and all other organizational entities within the Department of Defense
(hereafter referred to collectively as the “DoD Components”).
3. FUNCTIONS OF THE DEPARTMENT OF DEFENSE. As prescribed by higher authority,
the Department of Defense shall maintain and use armed forces to:
a. Support and defend the Constitution of the United States against all enemies, foreign and
domestic.
b. Ensure, by timely and effective military action, the security of the United States, its
possessions, and areas vital to its interest.
c. Uphold and advance the national policies and interests of the United States.
