Joe-1 (RDS-1, also called "First Lightning" by the Soviets) was the first Soviet nuclear test. It was detonated on August 29, 1949 at Semipalatinsk, Kazakhstan. It had a yield of 22 kilotons. Since that test the Western world has never felt completely safe.
It was similar to "The Gadget" and "Fat Man" nuclear bombs, in yield and design.