Intelligence can be a funny game sometimes. The first line of defence in protecting a nation’s secrets is to avoid drawing attention to their existence. If people do not know that a secret exists, then they will not spend time, energy and creativity figuring out how to get hold of it.
Unfortunately, what is not said can sometimes be just as problematic.
We now know that as early as 1941 the Soviet physicist Georgy Flerov noticed that the United States and Britain had stopped publishing anything to do with nuclear fission. Nuclear physics had moved pretty rapidly during the 1930s and in spring 1939, on the eve of war, the world press had briefly taken up the possibilities opened up by the nuclear chain reaction: unlimited electricity at low cost, a superbomb, and a submarine whose engine would not require oxygen.
Seeing that all had gone quiet on this particular front, Flerov realised that something was up and warned Stalin that to him this signified that the United States and Britain were engaged in research on atomic weapons. Stalin ordered the commencement of a Soviet program, which was derailed for a time by the German invasion, but by 1944 the Russians were engaged in the preparation of pure uranium and graphite, essential elements of their chosen route to a plutonium-based bomb. Information from Klaus Fuchs and Alan Nunn May helped to accelerate the program, which was given top priority following the first U.S. weapons test in the summer of 1945. In 1949 the Soviet Union conducted its first test of a nuclear weapon.
Source: Bertrand Goldschmidt, Atomic Rivals: a candid memoir of rivalries between among the Allies over the bomb, trans. George M. Temmer, Rutgers University Press, 1990.
Goldschmidt was a French Jewish chemist who had been Marie Curie’s laboratory assistant, escaped from Vichy France in April 1941, made his way to the United States, worked briefly on the United States program, and for the rest of the war worked on plutonium chemistry in Montreal. On his return to France he became director of chemistry at the new French Atomic Energy Commission (CEA) , and was subsequently for many years the French delegate to the International Atomic Energy Agency.