The Defense Threat Reduction Agency (DTRA) is both a defense agency and a combat support agency within the United States Department of Defense (DoD) for countering weapons of mass destruction and supporting the nuclear enterprise. Its stated mission is to provide "cross-cutting solutions to enable the Department of Defense, the United States Government, and international partners to Deter strategic attack against the United States and its allies; Prevent, reduce, and counter WMD and emerging threats; and Prevail against WMD-armed adversaries in crisis and conflict." DTRA is headquartered in Fort Belvoir, Virginia. The DTRA mission, organization and management, responsibilities and functions, relationships, authorities, and administration are defined in DoD Directive 5105.62, Defense Threat Reduction Agency (DTRA) .

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".