1958 US–UK Mutual Defence Agreement as an atomic spy, caused the proposal to be dropped. The June 1951 defection of Donald Maclean, who had served as a British member of the Combined Policy Committee from January 1947 to August 1948, reinforced the Americans' distrust of British security arrangements. The first British atomic bomb was successfully tested in Operation Hurricane on 3 October 1952, but although it was more advanced than the American bombs of 1946, Britain was still several years behind in nuclear weapons technology. The United States conducted Ivy Mike, the first nuclear test of a true thermonuclear device (also known as a hydrogen
1211th Test Squadron accomplished effectively with manned aircraft. Analyses of samples collected from atomic clouds were considered the most accurate method of determining the efficiency and yield of a nuclear device. Air Force Special Weapons Center (AFSWC) scientists accompanied the squadron on sampling missions in order to assess effects on humans. The Atomic Energy Commission (AEC) recommended that the USAF establish an organization specifically for gathering cloud samples. In 1953, HQ, USAF approved a test squadron for sampling atomic clouds; the squadron was titled the 4926th Test Squadron (Sampling) and assigned to the 4925th Test Group (Atomic). The new squadron was created within