The weapon was designed at the Kurchatov Institute, then at the time officially known as "Laboratory № 2" but designated as the "office" or "base" in internal documents, starting in April 1946. Plutonium for the bomb was produced at the industrial complex Chelyabinsk-40. , illustrating what he allegedly gave the Rosenbergs to pass on to the Soviet Union. That was later discovered to be part of the plans involved in the development of RDS-1. The RDS-1 explosion yielded 22 kilotons of TNT, similar to the US Gadget and Fat Man bombs. At Lavrentiy Beria's insistence, the RDS-1 bomb was designed as an implosion type weapon, similar to the Fat Man bomb dropped on Nagasaki, Japan; RDS-1 also had a solid plutonium core. The bomb designers had developed a more sophisticated design but rejected it because of the known reliability of the Fat Man type design, the Soviets having received extensive intelligence on the design of the Fat Man bomb during World War II, which was discovered in the espionage case of Julius and Ethel Rosenberg and during the Venona project. To test the effects of the new weapon, workers constructed houses made of wood and bricks, along with a bridge, and a simulated metro railway in the vicinity of the test site. Armoured hardware and approximately 50 aircraft were also brought to the testing grounds as well as over 1,500 animals to test the bomb's effects on life. The resulting data showed the RDS explosion to be 50% more destructive than originally estimated by its engineers. There are several explanations for the Soviet code-name of RDS-1, usually an arbitrary designation: a backronym "Special Jet Engine", or "Stalin's Jet Engine", or "Russia does it herself". Later weapons were also designated RDS but with different model numbers. Mikhail Pervukhin served as the chairman of the commission in charge of the RDS-1 testing. Five RDS-1 weapons were completed as a pilot series by March 1950 with a serial production of the weapon that began in December 1951.
The test surprised the Western powers. American intelligence had estimated that the Soviets would not produce an atomic weapon until 1953, while the British did not expect it until 1954. When the nuclear fission products from the test were detected by the U.S. Air Force, the United States began to follow the trail of the nuclear fallout debris. President Harry S. Truman notified the world of the situation on 23 September 1949: "We have evidence that within recent weeks an atomic explosion occurred in the U.S.S.R." Truman's statement likely in turn surprised the Soviets, who had hoped to keep the test a secret to avoid encouraging the Americans to increase their atomic programs, and did not know that the United States had built a test-detection system using the WB-29 Superfortress. The announcement was a turning point in the Cold War, that had just begun. Once the Soviet Union was confirmed to be in possession of the atomic bomb, pressure mounted to develop the first hydrogen bomb.
