The National Reconnaissance Office (NRO) helps the US practice the first rule of warfare: Know thine enemy. Called the "nation's eyes and ears in space," the Department of Defense agency designs, builds, and operates US reconnaissance satellites for the Central Intelligence Agency and the DoD. Information the agency gathers helps warn of potential trouble around the world, plan military operations, and monitor the environment. The NRO is comprised of 3,000 members from the Armed Services and CIA, as well as DoD civilian personnel. It works closely with the National Geospatial-Intelligence Agency and the National Security Agency, and is one of 17 agencies in the United States Intelligence Community.