The Central Intelligence Agency (CIA) is an independent civilian intelligence agency of the United States government. It is an executive agency and reports directly to the Director of National Intelligence, with responsibility for providing national security intelligence assessment to senior United States policymakers. Intelligence-gathering is performed by non-military commissioned civilian intelligence agents, many of whom are trained to avoid tactical situations. The CIA also oversees and sometimes engages in tactical and covert activities at the request of the President of the United States. Often, when such field operations are organized, the U.S. military or other warfare tacticians carry these tactical operations out on behalf of the agency while the CIA oversees them. Although intelligence-gathering is the agency's main agenda, tactical divisions were established in the agency to carry out emergency field operations that require immediate suppression or dismantling of a threat or weapon. The CIA's headquarters is located in Langley, McLean, Fairfax County, Virginia, a few miles west of Washington, D.C..