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 Arlington, most prominently the Antonin Scalia Law School of George Mason University. The area that now constitutes Arlington County was originally part of Fairfax County in the Colony of Virginia. Land grants from the British monarch were awarded to prominent Englishmen in exchange for political favors and efforts at development. One of the grantees was Thomas Fairfax, 6th Lord Fairfax of Cameron, who lends his name to both Fairfax County and the City of Fairfax. The county's name "Arlington" comes via Henry Bennet, Earl of Arlington, a Plantation along the Potomac River, and Arlington House, the family residence on that