The Pentagon is the headquarters building of the United States Department of Defense, in Arlington County, Virginia, across the Potomac River from Washington, D.C. The building was constructed on an accelerated schedule during World War II. As a symbol of the U.S. military, the phrase The Pentagon is often used as a metonym for the Department of Defense and its leadership.
A view of The Pentagon from the south in September 2007
The main Navy Building (foreground) and the Munitions Building were temporary structures built during World War I on the National Mall. The Department of War was headquartered in the Munitions Building for several years before moving into the Pentagon.
The Hall of Heroes on the Pentagon's main concourse
Military police keep back Vietnam War protesters during their sit-in at the Pentagon's National Mall entrance on 21 October 1967
United States Department of Defense
The United States Department of Defense is an executive branch department of the federal government of the United States charged with coordinating and supervising all agencies and functions of the U.S. government directly related to national security and the United States Armed Forces. As of June 2022, the U.S. Department of Defense is the largest employer in the world, with over 1.34 million active-duty service members, including soldiers, marines, sailors, airmen, and guardians. The Department of Defense also maintains over 778,000 National Guard and reservists, and over 747,000 civilians bringing the total to over 2.87 million employees. Headquartered at the Pentagon in Arlington County, Virginia, just outside Washington, D.C., the Department of Defense's stated mission is to provide "the military forces needed to deter war and ensure our nation's security".
President Truman signs the National Security Act Amendment of 1949
A December 2013 Department of Defense organizational chart
Joint Chiefs of Staff and Joint Staff organizational chart