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
Soviet atomic bomb project (including those now in Kazakhstan). The uranium for the Soviet nuclear weapons program came from mine production in the following countries, RDS-1, the first Soviet atomic test was internally code-named "First Lightning" ("Первая молния", or Pervaya Molniya) August 29, 1949, and was code-named by the Americans as "Joe 1". The design was very similar to the first US "Fat Man" plutonium bomb, using a TNT/hexogen implosion lens design. On September 24, 1951, the 38.3 kiloton device RDS-2 was tested based on a tritium "boosted" uranium implosion device with a levitated core. This test was code named "Joe 2" by the