The atmospheric tests conducted throughout the 1950s were critical to the definition of nuclear weapons effects for the design of survivable U.S. offensive and defensive weapons systems. Conducted under the auspices of the AEC, each test series was directed by a Joint Task Force appointed by the JCS. In early nuclear test series, the USAF assembled one Air Task Group per test to perform air support and missions. The frequency of tests and these issues justified a permanent group, and the USAF looked to AFSWC to fill the requirements. In response, in 1956 AFSWC established the 4950th Test Group (Nuclear) to serve as a permanent USAF Air Task Group for atmospheric testing, replacing the 4925th Test Group (Atomic), which then focused on the aircraft/weapon marriage mission.