The cold war distorted definitions of 'normal' nuclear behaviour. The giant antagonists, the United States and the Soviet Union, built gargantuan arsenals poised for launch at a moment's notice. They poked and prodded each other until the Cuban missile crisis of 1962 chastened them to give arms control a chance. Notwithstanding a series of treaties meant to manage their nuclear competition and help shape a global nuclear order — from the Partial Test Ban Treaty in 1963 through to the Strategic Arms Reduction Treaty II 30 years later — Washington DC and Moscow ordered the construction of thousands more nuclear weapons and kept them ready for use, even when no crisis was at hand.

By the mid-1970s, China, Israel and India had nuclear explosives, and Pakistan and South Africa were preparing to join them. These nations treated nuclear weapons differently. They built relatively few, did not deploy them for immediate use and kept them largely out of political view. South Africa disarmed in the early 1990s, and North Korea became nuclear-armed. Of the nine countries that have nuclear weapons today, the United States and Russia are hardly typical.

Read the full article in Nature.