Britain’s Thermonuclear Bluff
Norman Dombey and Eric Grove, 22 October 1992
“... megaton were tested. In August 1953 the Soviet Union exploded a large nuclear weapon, known in the West as Joe-4, which it announced was thermonuclear. US weapon scientists have known for some time, however, that the yield of Joe-4 was only about 200-300 kilotons and that it was therefore unlikely to have been a hydrogen bomb in the Ulam-Teller sense. This has ... ”