Nuclear weapons program of the Soviet Union

Soviet atomic bomb project
Russian physicists Andrei Sakharov (left) and Igor Kurchatov, who led the program to success.
Operational scope	Operational R&D
Location	Atomgrad, Semipalatinsk, Chagan Lake
Planned by	NKVD, NKGB GRU, MGB, PGU
Date	1940–49
Executed by	Soviet Union
Outcome	The successful development of nuclear weapons.

The Soviet atomic bomb project (Russian: Советский проект атомной бомбы, Sovetskiy proyekt atomnoy bomby) was the classified research and development program that was authorized by Joseph Stalin in the Soviet Union to develop nuclear weapons during World War II.

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. 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.