Joe-1, the American nickname for the first Soviet atomic test, referred to Joseph Stalin. * Image: Courtesy of Stepanovas * 1949: The Soviet Union explodes its first nuclear weapon at its testing range on the Kazakhstan steppe. Many historians consider the test the beginning of the nuclear arms race.
Known as "First Lightning" to the Russians and "Joe-1" (a cheeky reference to Joseph Stalin) to the Americans, the weapon had roughly the equivalent in yield to the atomic bomb the United States had dropped on Nagasaki four years earlier. The successful Soviet test came as a profound shock to the West. U.S. intelligence believed that the Soviet Union was at least several years away from being able to detonate a nuclear device.
That progress had been accelerated, thanks in part to physicist Klaus Fuchs and other scientists who were members of an effective Soviet spy ring inside the U.S. nuclear program. Fuchs, a German émigré who became a British subject before joining the Manhattan Project in 1943, had been passing British and American nuclear secrets to Moscow since the German invasion of the USSR in 1941, believing the Soviets had the right to know what their allies were up to.
The extent of Soviet penetration into their rival's nuclear program wasn't fully appreciated until January 1950, when Fuchs, under prolonged questioning by British intelligence, finally cracked. His confession to MI5 also implicated Harry Gold, a naturalized American who later admitted to acting as a Soviet courier on Fuchs' behalf. Gold would later be a key witness in the trial of Julius and Ethel Rosenberg.
Some Soviet nuclear scientists have long downplayed the value of Fuchs' information, maintaining that it was the lack of uranium, and not the knowledge of what to do with it, that caused the U.S.S.R. to lag at the beginning. In fact, Soviet nuclear research, even without an assist from the so-called Atomic Spies, was already advanced.