The birth of U.S. UAVs (called RPVs at the time) began in 1959 when United States Air Force (USAF) officers, concerned about losing pilots over hostile territory, began planning for the use of unmanned flights.[5] This plan became intensified when Francis Gary Powers and his "secret" U-2 were shot down over the Soviet Union in 1960. Within days, the highly classified UAV program was launched under the code name of "Red Wagon".[6] The August 2 and August 4, 1964, clash in the Tonkin Gulf between naval units of the U.S.