United States Department of Defense

United States Department of Defense
United States Department of Defense Seal.svg
Agency overview
Formed18 September 1947; 71 years ago (1947-09-18) (as National Military Establishment)
Preceding agencies
TypeExecutive department
JurisdictionU.S. federal government
HeadquartersThe Pentagon
Arlington, Virginia, U.S.
38°52′16″N 77°3′21″W / 38°52′16″N 77°3′21″W / 38.87111; -77.05583
Employees732,079 (civilian)[1]
1,300,000 (active duty military)
826,000 (National Guard and reserve):2.86 million total[2] (2018)
Annual budget$717 billion (2019)[3]
Agency executives
Child agencies

The Department of Defense (DoD,[4] USDOD, or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government concerned directly with national security and the United States Armed Forces. The department is the largest employer in the world,[5] with nearly 1.3 million active duty servicemen and women[a] as of 2016.[6] Adding to its employees are over 826,000 National Guardsmen and Reservists from the four services,[b] and over 732,000 civilians[7] bringing the total to over 2.8 million employees.[2] Headquartered at the Pentagon in Arlington, Virginia, just outside Washington, D.C., the DoD's stated mission is to provide "the military forces needed to deter war and ensure our nation's security".[8][9]

The Department of Defense is headed by the Secretary of Defense, a cabinet-level head who reports directly to the President of the United States. Beneath the Department of Defense are three subordinate military departments: the United States Department of the Army, the United States Department of the Navy, and the United States Department of the Air Force. In addition, four national intelligence services are subordinate to the Department of Defense: the Defense Intelligence Agency (DIA), the National Security Agency (NSA), the National Geospatial-Intelligence Agency (NGA), and the National Reconnaissance Office (NRO). Other Defense Agencies include the Defense Advanced Research Projects Agency (DARPA), the Defense Logistics Agency (DLA), the Missile Defense Agency (MDA), the Defense Health Agency (DHA), Defense Threat Reduction Agency (DTRA), the Defense Security Service (DSS), and the Pentagon Force Protection Agency (PFPA), all of which are under the command of the Secretary of Defense. Additionally, the Defense Contract Management Agency (DCMA) provides acquisition insight that matters, by delivering actionable acquisition intelligence from factory floor to the warfighter. Military operations are managed by ten regional or functional Unified combatant commands. The Department of Defense also operates several joint services schools, including the National Defense University (NDU) and the National War College (NWC).


The history of the defense of the United States started with the Continental Congress in 1775. The creation of the United States Army was enacted on 14 June 1775.[10] This coincides with the American holiday Flag Day. The Second Continental Congress would charter the United States Navy, on 13 October 1775,[11] and create the United States Marine Corps on 10 November 1775.

The War Department and Navy Department

The Preamble of the United States Constitution gave the authority to the federal government to defend its citizens:

We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.

— Constitution of the United States

Upon the seating of the first Congress on 4 March 1789, legislation to create a military defense force stagnated as they focused on other concerns relevant to setting up the new government. President George Washington went to Congress to remind them of their duty to establish a military twice during this time. Finally, on the last day of the session, 29 September 1789, Congress created the War Department, historic forerunner of the Department of Defense.[12][13] The War Department handled naval affairs until Congress created the Navy Department in 1798. The secretaries of each of these departments reported directly to the president as cabinet-level advisors until 1949, when all military departments became subordinate to the Secretary of Defense.

National Military Establishment

President Harry Truman signs the National Security Act Amendment of 1949

After the end of World War II, President Harry Truman proposed creation of a unified department of national defense. In a special message to Congress on 19 December 1945, the President cited both wasteful military spending and inter-departmental conflicts. Deliberations in Congress went on for months focusing heavily on the role of the military in society and the threat of granting too much military power to the executive.[14]

On 26 July 1947, Truman signed the National Security Act of 1947, which set up a unified military command known as the "National Military Establishment", as well as creating the Central Intelligence Agency, the National Security Council, National Security Resources Board, United States Air Force (formerly the Army Air Forces) and the Joint Chiefs of Staff. The act placed the National Military Establishment under the control of a single Secretary of Defense.[15][16][17] The National Military Establishment formally began operations on 18 September, the day after the Senate confirmed James V. Forrestal as the first Secretary of Defense.[16] The National Military Establishment was renamed the "Department of Defense" on 10 August 1949 and absorbed the three cabinet-level military departments, in an amendment to the original 1947 law.[18]

Under the Pub.L. 85–599), channels of authority within the department were streamlined, while still maintaining the ordinary authority of the Military Departments to organize, train and equip their associated forces. The Act clarified the overall decision-making authority of the Secretary of Defense with respect to these subordinate Military Departments and more clearly defined the operational chain of command over U.S. military forces (created by the military departments) as running from the president to the Secretary of Defense and then to the unified combatant commanders. Also provided in this legislation was a centralized research authority, the Advanced Research Projects Agency, eventually known as DARPA. The act was written and promoted by the Eisenhower administration, and was signed into law 6 August 1958.

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srpskohrvatski / српскохрватски: Ministarstvo obrane Sjedinjenih Američkih Država