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 property. (Ultimately, the name is a variant of Harlington, London, seat of the first Baron of Arlington; it in turn derives from Hygerǣd, an Anglo-Saxon noble's name.) George Washington Parke Custis, grandson of First Lady Martha Washington, acquired this land in 1802. The estate was eventually passed down to Mary Anna Custis Lee, wife of General Robert E. Lee. The property later became Arlington National Cemetery during the American Civil War, and eventually lent its name to present-day Arlington County. The area that now contains Arlington County was ceded to the new United States federal government by Virginia. With the