Although the Soviet scientific community discussed the possibility of an atomic bomb throughout the 1930s, going as far as making a concrete proposal to develop such a weapon in 1940, the full-scale program was initiated only in response to the intelligence reports collected by Soviet intelligence through their spy ring in the United States on the secretive Manhattan Project.
Because of the conspicuous silence of the scientific publications on the subject of nuclear fission by German, American, and British scientists, Russian physicist Georgy Flyorov suspected that the Allied powers had secretly been developing a "superweapon" since 1939. Flyorov wrote a letter to Stalin urging him to start this program in 1942.:78–79 Initial efforts were slowed due to the German invasion of the Soviet Union and remained largely composed of the intelligence knowledge gained from the spy rings working in the U.S.' Manhattan Project in 1943.
After learning of the atomic bombings of Hiroshima and Nagasaki that ended the Pacific War in 1945, the program was aggressively pursued, mainly through effective intelligence gathering about the German weapon project and the American Manhattan Project. The Russian efforts also rounded up captured German scientists to join their program, and relied heavily on knowledge passed by the spy ring to the Russian intelligence agencies.:242–243
As early as 1910 in Russia, independent research was being conducted on radioactive elements by several Russian scientists.:44:24–25 Despite the hardship faced by the Russian academy of sciences during the national revolution in 1917, followed by the violent civil war in 1922, the Russian scientists had made remarkable efforts towards the advancement of physics research in the Soviet Union in the 1930s.:35–36 Before the first revolution in 1905, the mineralogist Vladimir Vernadsky had made a number of public calls for a survey of Russia's uranium deposits but none were heeded.:37