It was detonated on 29 August 1949 at 7:00 a.m.,[2] at the Semipalatinsk Test Site, Kazakh SSR,[3] after top-secret research and development as part of the Soviet atomic bomb project.

[citation needed] There are several explanations for the Soviet code-name of RDS-1, usually an arbitrary designation: a backronym "Special Jet Engine" (Реактивный двигатель специальный, Reaktivnyi Dvigatel Spetsialnyi), or "Stalin's Jet Engine" (Реактивный двигатель Сталина, Reaktivnyi Dvigatel Stalina), or "Russia does it herself" (Россия делает сама, Rossiya Delayet Sama).

[6] The RDS-1 explosive yield was 22 kilotons TNT equivalent, similar to the US Gadget and Fat Man bombs.

[11] Some United States Air Force WB-29 weather reconnaissance aircraft were fitted with special filters to collect atmospheric radioactive debris.

[14] 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."[15] 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.