HIS: This Day in History: 1949 – Soviet atomic bomb project: The Soviet Union tests its first atomic bomb, known as First Lightning or Joe 1, at Semipalatinsk, Kazakhstan.

HIS: This Day in History: 1949 – Soviet atomic bomb project: The Soviet Union tests its first atomic bomb, known as First Lightning or Joe 1, at Semipalatinsk, Kazakhstan.

The Soviet atomic bomb project 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 wasn't initiated until World War II.

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 Soviet spy rings working in the U.S. Manhattan Project.

After Stalin learned of the atomic bombings of Hiroshima and Nagasaki, the program was pursued aggressively and accelerated through effective intelligence gathering about the German nuclear weapon project and the American Manhattan Project. The Soviet efforts also rounded up captured German scientists to join their program, and relied on knowledge passed by spies to Soviet intelligence agencies.

On 29 August 1949, the Soviet Union secretly conducted its first successful weapon test (First Lightning, based on the American "Fat Man" design) at the Semipalatinsk Test Site in Kazakhstan.