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,
Organizational structure of the United States Department of Defense candidate John McCain in New Hampshire, seven on-duty uniformed Army personnel addressed the gathering. As another example, although DOD Directive 1344.10 prohibits political appearances by active-duty military members in uniform, Virginia Governor Bob McDonnell invited a uniformed Army Staff Sergeant to stand behind him during his televised Republican response to the 2010 State of the Union Address. Defense Agencies are established as DoD Components by law, the President, or the Secretary of Defense to provide for the performance, on a DoD-wide basis, of a supply or service activity that is common to more than one Military Department when it is