United States Department of Defense United States Department of Defense The Department of Defense (DoD, 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, with nearly 1.3 million active duty servicemen and women as of 2016. Adding to its employees are over 826,000 National Guardsmen and Reservists from the four services, and over 742,000 civilians bringing the total to over 2.8 million employees. Headquartered at the Pentagon in Arlington, Virginia,
Arlington County, Virginia federal territory, including the cities of Washington, Georgetown, and Alexandria, under the exclusive control of Congress. Further, the unincorporated territory within the District was organized into two counties: the County of Washington to the east of the Potomac and the County of Alexandria to the west. It included all of the present Arlington County, plus part of what is now the independent city of Alexandria. This Act formally established the borders of the area that would eventually become Arlington but the citizens located in the District were no longer considered residents of Maryland or Virginia, thus ending their representation in