The USSR had its own nuclear program almost three years before the bombing of Hiroshima. Soviet agents in America learned of the Manhattan Project as early as 1941. This information was passed to Moscow, which initiated research into nuclear weapons the following year. In 1945 Soviet spies obtained information of immense importance: American diagnostic plans and blueprints for a nuclear weapon. These plans allowed the fast-tracking of Soviet nuclear weapons technology. In August 1949, the Russians detonated their first prototype nuclear weapon. Code-named ‘First Lightning’ by the Russians and ‘Joe 1’ by the Americans, it was similar in design, appearance and yield to the ‘Fat Man’ bomb that had decimated Hiroshima.
Within six years Soviet nuclear physicists had test-fired several nuclear weapons, each more elaborate and powerful than their predecessors. In 1955 they air-dropped a hydrogen bomb with a yield of 1.6 megatons, capable of utterly destroying a city of one million people. Both the US and the USSR also had sizeable missile programs, which used parallel technology to their research into space exploration. By the late 1950s both countries had developed intercontinental ballistic missiles (ICBMs), a frightening new technology that allowed the long-range delivery and detonation of nuclear warheads. ICBMs were more cost-effective than aircraft, and unlike bombers they were almost impossible to intercept. They were also much faster: an ICBM could be launched into sub-orbital flight from a missile silo before hitting targets halfway around the globe in less than 45 minutes. Shorter range missiles could be launched from battleships and submarines, further reducing response times.