<human>:  When did the Soviet Union start to develop nuclear weapons?
<bot>: The Soviet Union started to develop nuclear weapons in the 1940s. The first Soviet nuclear weapon was tested in 1949. The Soviet Union also developed a number of intercontinental ballistic missiles (ICBMs), which are missiles that can travel to the other side of the world. ICBMs are very important because they can deliver nuclear weapons very far away from their launch site.