About the Department of Defense (DoD)

On behalf of the Secretary of Defense and Deputy Secretary of Defense, we welcome you to Defense.gov, the official web site for the Department of Defense and the starting point for finding U.S. military information online. The home page for this site is located at http://www.defense.gov/.

The Secretary of Defense is the principal defense policy advisor to the President. Under the direction of the President, the Secretary exercises authority, direction, and control over the Department of Defense. The Deputy Secretary, the second-highest ranking official in the DoD, is delegated full power and authority to act for the Secretary and to exercise the powers of the Secretary on any and all matters for which the Secretary is authorized to act.

The Department of Defense is America's oldest and largest government agency. With our military tracing its roots back to pre-Revolutionary times, the Department of Defense has grown and evolved with our nation.

Today, the Department, headed by Secretary of Defense Jim Mattis, is not only in charge of the military, but it also employs a civilian force of thousands. With over 1.3 million men and women on active duty, and 742,000 civilian personnel, we are the nation's largest employer. Another 826 thousand serve in the National Guard and Reserve forces. More than 2 million military retirees and their family members receive benefits.

Headquarters of the Department of Defense, the Pentagon is one of the world's largest office buildings. It is twice the size of the Merchandise Mart in Chicago, and has three times the floor space of the Empire State Building in New York. Built during the early years of World War II, it is still thought of as one of the most efficient office buildings in the world. Despite 17.5 miles of corridors it takes only seven minutes to walk between any two points in the building.

The national security depends on our defense installations and facilities being in the right place, at the right time, with the right qualities and capacities to protect our national resources. Those resources have never been more important as America fights terrorists who plan and carry out attacks on our facilities and our people. Our military servicemembers and civilians operate in every time zone and in every climate. More than 450,000 employees are overseas, both afloat and ashore.

The Defense Department manages an inventory of installations and facilities to keep Americans safe. The Department’s physical plant is huge by any standard, consisting of more than several hundred thousand individual buildings and structures located at more than 5,000 different locations or sites. When all sites are added together, the Department of Defense utilizes over 30 million acres of land.

These sites range from the very small in size such as unoccupied sites supporting a single navigational aid that sit on less than one-half acre, to the Army's vast White Sands Missile Range in New Mexico with over 3.6 million acres, or the Navy’s large complex of installations at Norfolk, Virginia with more than 78,000 employees.

Mission

The mission of the Department of Defense is to provide the military forces needed to deter war and to protect the security of our country. The department's headquarters is at the Pentagon.

The mission of Defense.gov is to support the overall mission of the Department of Defense by providing official, timely and accurate information about defense policies, organizations, functions and operations. Also, Defense.gov is the single, unified starting point for finding military information online.

This mission is consistent with the DoD Principles of Information, which outline the Department's policy for providing information to military members, DoD civilians, military family members, the American public, the Congress, and the news media. The information you find here is cleared for public release in accordance with applicable DoD policies.

History

The Army, Navy, and Marine Corps were established in 1775, in concurrence with the American Revolution. The War Department was established in 1789, and was the precursor to what is now the Department of Defense.

One year later, in 1790, the Coast Guard (part of Homeland Security in peace time) was established. This was followed by the founding of the Department of the Navy in 1798.

The decision to unify the different services under one Department led to the creation of the National Military Establishment in 1947. This establishment would replace the War Department, which converted to the Department of the Army. That same year, the U.S. Air Force was established followed by the founding of the Department of the Air Force.

Finally, the three military branches, Army, Navy, and Air Force, were placed under the direct control of the new Secretary of Defense, confirmed by Senate.

In 1949, an amendment to the National Security Act further consolidated the national defense structure by withdrawing cabinet-level status from the three Service secretaries. The National Military Establishment was then renamed the Department of Defense.

Current as of Jan 27, 2017.