US, had been developed for past 9 years until release was made apparent to public in 1945.
Stalin congratulated but was angry about miscommunication and why Stalin couldn't be trusted, but it was highly likely he had spies listening in the US so awareness of the bomb before it was made public is likely.
when did soviets bring in their atomic bomb?
1949
why is this an issue?
due to Sovietunion catching up as a superpower US worry about truestrength of both blocs
started series of events (arms and space race) with MAD