Extinction.

It is tempting to think that it would be cheaper and more effective to have distant allies like Germany or South Korea or Saudi Arabia rather than link their security to U.S. forces, bases, and assurances. Nuclear theorists like Kenneth Waltz to the so-called “pacifying” effects of nuclear weapons, saying their existence makes states “exceedingly cautious” and therefore less likely to fight similarly-armed opponents. If more countries had the bomb, the logic goes, fewer wars would occur. But countries do not obtain the bomb in a vacuum. The nuclear posture and strategic decisions of nuclear-armed nations have a significant, often immediate, impact on the nuclear acquisition decisions of other nations. More simply: If your adversary or your neighbor goes nuclear, you will, too. There is nothing automatic about the nuclear domino theory, and it has been successfully countered in some regions, but the theory is generally correct. The Soviet Union got the bomb because, as Stalin his scientists after Hiroshima, “The balance has been broken. Build the bomb. It will remove the great danger from us.” Britain and France got the bomb because the Soviets (and the U.S.) had it. China did the same, then India got the bomb because China did; Pakistan because India did. Nuclear competition in Asia would not end if South Korea decided to build a nuclear arsenal. Others in the region would likely follow suit. Japan, Taiwan, perhaps Vietnam. Similarly, a Saudi bomb would likely beget an Iranian bomb, a Turkish bomb and even an Egyptian bomb. Far from making the region — and the United States — safer, these arms races would blanket the globe with nuclear tripwires, each primed to unleash unprecedented destruction at the slightest twitch.