Updated November 28, 2018
Defense Primer: The Military Departments
The Department of Defense (DOD) is comprised of three
States; and members or units of the state-level Army
military departments: the Department of the Army, the
National Guard when ordered into the service of the United
Department of the Navy, and the Department of the Air
States.
Force. The organization of each military department is
outlined in Title 10 of the United States Code.
The Secretary of the Army, as assisted by the Office of the
Secretary of the Army, has responsibility for all affairs of
The term military department refers to a department’s
the Army. The Chief of Staff of the Army, as assisted by
senior civilian official and senior military officer, as well as
the Army Staff, provides military advice to the Secretary of
all departmental headquarters staff offices, field
the Army.
headquarters, armed forces, reserve components, civilian
employees, installations, activities, and functions under the
The Department of the Navy
control or supervision of the department’s senior officials.
The Department of the Navy has authorities and
Each department is organized under the leadership of a
responsibilities relating to two military service branches:
Secretary, a civilian official appointed by the President with
the Navy and the Marine Corps.
the advice and consent of the Senate. The three department
The mission statement of the Navy is to “maintain, train
secretaries all carry out the functions of their positions
and equip combat-ready Naval forces capable of winning
under the authority, direction, and control of the Secretary
wars, deterring aggression and maintaining freedom of the
of Defense.
seas.” The Marine Corps is an “expeditionary force in
The term armed forces refers to the five U.S. military
readiness” statutorily tasked with using combined arms
service branches: the Army, the Navy, the Air Force, the
forces to seize or defend forward-positioned naval bases,
Marine Corps, and the Coast Guard. While the Coast Guard
and conducting land operations in support of naval
is statutorily considered to be a military service, it generally
campaigns.
operates under Title 14 authorities. Title 14 states that the
Coast Guard “shall be a service in the Department of
Unlike the Departments of the Army and the Air Force, the
Department of the Navy’s organizational structure is
Homeland Security, except when operating as a service in
the Navy” upon the declaration of war, if so directed by
specifically defined by law to include:
Congress in the declaration, or upon the direction of the
Senior civilian and military leadership and
President (see Section 3 of Title 14, U.S. Code).
headquarters staff offices;
All operating forces of the Navy and the Marine Corps;
Figure 1. Organizational Structure of DOD Military
The reserve components of the Navy and the Marine
Departments
Corps; and
All functions, organizations, forces, activities, and
facilities under the control or supervision of the senior
civilian official of the Department of the Navy
The Secretary of the Navy, as assisted by the Office of the
Secretary of the Navy, has responsibility for all affairs of
the Navy and the Marine Corps. The Chief of Naval
Operations, as assisted by the Office of the Chief of Naval
Operations, and the Commandant of the Marine Corps, as
assisted by the Headquarters, Marine Corps, both provide
military advice to the Secretary of the Navy.
The Department of the Air Force
The mission statement of the Air Force is to “fly, fight and
Source: CRS illustration
win” as it carries out operations in air, space, and
cyberspace. The Air Force, operating as a military service
The Department of the Army
within the Department of the Air Force, consists of the
The mission statement of the Army is to “fight and win our
Regular Air Force; the Air Force Reserve; the Air National
Nation’s wars by providing prompt, sustained land
Guard of the United States; and members or units of the
dominance across the full range of military operations and
state-level Air National Guard ordered into the service of
spectrum of conflict in support of combatant commanders.”
the United States.
The Army, operating as a military service within the
Department of the Army, consists of the Regular Army; the
The Secretary of the Air Force, as assisted by the Office of
Army Reserve; the Army National Guard of the United
the Secretary of the Air Force, has responsibility for all
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Defense Primer: The Military Departments
affairs of the Air Force. The Chief of Staff of the Air Force,
Each service chief is also designated as a member of the
assisted by the Air Staff, provides military advice to the
Joint Chiefs of Staff (JCS). Led by the Chairman of the
Secretary of the Air Force.
Joint Chiefs of Staff (CJCS), the JCS offers advice to the
President, the National Security Council, the Homeland
Departmental Civilian Leadership and Staff
Security Council, and the Secretary of Defense on military
By law, a department secretary has the responsibility and
issues. By law, a service chief provides service-specific
authority to conduct all affairs of a military department,
advisory support to the department secretary through
including recruiting, training, equipping, mobilization, and
functions such as:
personnel administration. Each secretary has responsibility
Overseeing the operations of military headquarters staff;
for developing department-specific policies and programs
Relaying the plans and recommendations of military
consistent with broader national security objectives, while
headquarters staff to the secretary; and
also internally implementing all department-specific policy,
Acting as the executive agent of the secretary in
program, and budget decisions of the President or the
carrying out such plans and recommendations.
Secretary of Defense. Secretaries are also tasked with
ensuring effective cooperation and coordination between
the military departments and DOD agencies; supporting the
A vice service chief and varying numbers of deputy service
current and future operational requirements of the
chiefs and assistant service chiefs report to and assist the
combatant commands; and supervising and controlling the
service chief in formulating service-specific plans and
intelligence activities of a department.
recommendations. The vice service chief, appointed by the
President with the advice and consent of the Senate, is the
An Under Secretary, and a varying number of Assistant
second-highest ranking military officer in the department. A
Secretaries, report to and assist the secretary in managing
department’s deputy and assistant service chiefs, active-
the operations of a department. The Under Secretary is the
duty officers detailed to the positions by the secretary
second-highest ranking civilian official in a department. All
concerned, operate under the supervision of the vice service
Under Secretaries and Assistant Secretaries are civilian
chief.
officials appointed by the President with the advice and
Within each department, the service chief leads a military
consent of the Senate.
headquarters staff element that reports to and provides
While the exact number and functions of the Assistant
professional assistance to the departmental secretary for
Secretaries varies by department, each department has an
matters relating to a specific armed service. A military
Assistant Secretary to oversee manpower and reserve
headquarters staff element is responsible to the Secretary
component affairs; an Assistant Secretary to oversee
for functions such as training, equipping, and mobilization
departmental comptroller operations, including financial
of the service’s operating forces; monitoring and reporting
management; and an Assistant Secretary to oversee
on the service’s operating efficiency; and coordinating the
acquisition-related matters.
actions of service-level components.
The Under Secretary is the head of the departmental Office
Relevant Statutes
of the Secretary, a civilian headquarters staff element
tasked with assisting the secretary in carrying out the
Title 10, U.S. Code, Subtitle B, Part I
responsibilities of the position. The Office of the Secretary
Title 10, U.S. Code, Subtitle C, Part I
is responsible for exercising functions such as acquisition,
Title 10, U.S. Code, Subtitle D, Part I
auditing, information management, comptroller operations,
legislative affairs, and public affairs within the
departmental military and civilian headquarters staff
CRS Products
elements.
CRS In Focus IF10543, Defense Primer: The Department of
Departmental Military Leadership and Staff
Defense, by Kathleen J. McInnis
A service chief is a senior military officer designated as the
CRS In Focus IF10544, Defense Primer: Department of the Army
principal military advisor to a departmental secretary for
and Army Command Structure, by Barbara Salazar Torreon and
matters relating to a specific armed service. While a service
Andrew Feickert
chief is appointed by the President with the advice and
CRS In Focus IF10484, Defense Primer: Department of the Navy,
consent of the Senate, he or she performs his or her duties
by Ronald O'Rourke
under the authority, direction, and control of the
CRS In Focus IF10547, Defense Primer: The United States Air
departmental secretary concerned, and is directly
Force, by Jeremiah Gertler
responsible to that secretary.
CRS In Focus IF10542, Defense Primer: Commanding U.S.
The four service chiefs – the Army Chief of Staff, the Chief
Military Operations, by Kathleen J. McInnis
of Naval Operations, the Commandant of the Marine Corps,
and the Air Force Chief of Staff – do not have operational
command authority over their respective armed services.
Nevertheless, as authorized by a departmental secretary, a
Heidi M. Peters, Analyst in U.S. Defense Acquisition
service chief does exercise supervision over an armed
Policy
service’s major commands and agencies, consistent with the
authority assigned to the combatant commanders of the
IF10550
unified or specified combatant commands.
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Defense Primer: The Military Departments
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress.
Information in a CRS Report should not be relied upon for purposes other than public understanding of information that has
been provided by CRS to Members of Congress in connection with CRS’s institutional role. CRS Reports, as a work of the
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reproduced and distributed in its entirety without permission from CRS. However, as a CRS Report may include
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