British intelligence and the Soviet atomic bomb, 1945–1950

Abstract

With relations with the Soviet Union growing ever ‘hotter’, it became essential for the British to comprehend Soviet atomic development. However, British intelligence had to rely on more overt methods of intelligence collection, which provided an inadequate basis from which to proceed. This was further hindered by the interpretation of such information on the basis of Anglo-American development and by the 1946 McMahon Act. Accordingly the first Soviet atomic bomb in August 1949 was not accurately predicted by the British. Meanwhile British war planning centred on the year 1957, based – it was argued – on strategic forecasts. Yet the impact of recently released intelligence material throws this into question, and instead reveals that the date reflected British war readiness, rather than when British intelligence predicted the Soviet Union would have achieved the nuclear capability to wage a successful war.