In The Better Angels of Our Nature, Steven Pinker writes:
Finally, the nuclear peace theory cannot explain why the wars that did take place often had a nonnuclear force provoking (or failing to surrender to) a nuclear one — exactly the matchup that the nuclear threat ought to have deterred. North Korea, North Vietnam, Iran, Iraq, Panama and Yugoslavia defied the United States; Afghan and Chechen insurgents defied the Soviet Union; Egypt defied Britain and France; Egypt and Syria defied Israel; Vietnam defied China; and Argentina defied the United Kingdom. For that matter the Soviet Union established its stranglehold on Eastern Europe during just those years (1945-490) when the United States had nuclear weapons and it did not. They correctly anticipated that for anything but an existential danger, the implicit threat of a nuclear response was a bluff. The Argentinian junta ordered the invasion of the Falkland Islands in full confidence that Britain would not retaliate by reducing Buenos Aires to a radioactive crater. Nor could Israel have creditably threatened the amassed Egyptian armies in 1967 or 1973, to say nothing of Cairo.
Pinker’s argument here is a powerful one, and should be taken into account by the dangerous fools who are now trying to lie us into another war, this time to save ourselves from atomic annihilation at the hands of Iran. But that country’s so far imaginary nuclear bomb would not be aimed at us. The Iranians would see it as comforting (although unusable) insurance against Israel’s equally nonthreatening nuclear capability. That capability, we should not forget, was at best unopposed by the United States back in the 60s. At worst, it was encouraged, even facilitated, by Washington.