After the atomic bombings of Hiroshima and Nagasaki, the USSR utilized intelligence gathered from the German nuclear weapons project and the American Manhattan Project to aggressively pursue the development of a Russian atomic bomb.

In August 1949, the Soviet Union secretly conducted its first successful weapon test 

Although President Harry Truman announced in September 1949, that there had been an atomic explosion in Russia, he did not say specifically that it was an atom bomb that had been exploded.

In October 1951 Josef Stalin acknowledged that the USSR had an atomic bomb