When considering the dangers of an Iranian nuclear weapons program, those who differ on political ideology find rare common ground. According to nearly everyone, if Iran develops nuclear weapons, its neighbors will inevitably do so, too. Former U.S. Senator Sam Nunn (D-Ga.), for example, said earlier this year, "The governments of the world must understand what a threat it is if the Iranians get nuclear weapons, because there are probably 10 other countries in the Middle East over the next 10 to 20 years that would follow down that road." U.S. policymakers from John Bolton, the conservative former U.S. ambassador to the UN, to Vice President Joe Biden all seem to agree with this dark prediction.
But there's one problem with this "nuclear domino" scenario: the historical record does not support it. Since the dawn of the nuclear age, many have feared rapid and widespread nuclear proliferation; 65 years later, only nine countries have developed nuclear weapons. Nearly 20 years elapsed between the emergence of the first nuclear state, the United States, in 1945, and the fifth, China, in 1964.
The next 40 years gave birth to only five additional nuclear countries: India, Israel, South Africa, Pakistan, and North Korea. South Africa voluntarily disarmed in the 1990s, as did Belarus, Kazakhstan, and Ukraine following the dissolution of the Soviet Union. After Israel developed a nuclear weapons capability in the late 1960s, no regional nuclear chain reaction followed, even though the country is surrounded by rivals. Nor was there even a two-country nuclear arms race in the region.
Similarly, it has now been four years since North Korea became a nuclear weapons state, yet South Korea and Japan have not followed suit, despite the fact that they have a latent nuclear weapons capability -- access to the fissile material necessary for nuclear weapons. These countries' decisions to not go nuclear are largely thanks to extensive U.S. efforts to dissuade them. Both South Korea and Japan enjoy firm and long-standing security assurances from Washington, including protection under the U.S. strategic nuclear umbrella, obviating the need for their own deterrents. Following North Korea's 2006 nuclear test, U.S. President George W. Bush immediately assured South Korea and Japan that the United States was unequivocally committed to protecting them...