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In the late 1950s, Soviet leader Nikita Khrushchev turned down Chinese leader Mao Zedung’s request to help his country build an atomic bomb, although the Soviet Union initially helped China several years earlier. The Kremlin also did not share its atomic secrets with another key Cold War ally — East Germany. Now that the Cold War a thing of the past, Russia is even more interested in stopping the proliferation of nuclear weapons. The prospect of a nuclear Iran bodes ill not only for Russia, but for the entire world. Iran’s example would only inspire other regional powers to acquire nuclear weapons in the Middle East powder keg. What’s more, it would only be a matter of time before terrorists of all stripes got their hands on enough nuclear bombs to hold all...