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
Operation Tumbler–Snapper Operation Tumbler–Snapper Operation Tumbler–Snapper was a series of atomic tests conducted by the United States in early 1952 at the Nevada Test Site. The "Tumbler-Snapper" series of tests followed "Operation Buster-Jangle", and preceded "Operation Ivy". The "Tumbler" phase, sponsored by the Atomic Energy Commission consisted of three airdrops which were intended to help explain discrepancies in the actual and estimated blast shock wave damage noted on previous detonations, and to establish more accurately the optimum height of burst. The "Snapper" phase, sponsored by the Department of Defense consisted of one airdrop and four tower shots intended to test various new