If nuclear weapons had never been developed, one could make a plausible case that the Cold War would not have stayed cold, that history might have evolved in very different ways because calculations would have been very different.

India and Pakistan now represent two of the world’s nine nuclear weapon states. India first tested a nuclear device in 1974, in part as a response to China’s development of nuclear weapons. India and China fought a short war in 1962 that China won easily, and the two continue to view each other warily. The border between them remains in dispute, de

Neither country would start a war with a big bomb. But would they launch a small one? Probably. And would a small bomb justify retaliating with a big one? Yes. So the small bombs increased the odds of the big bombs being used. Small risks weren’t the alternative to big risks; they were the trigger.