In late 1961 the Soviet leader, Nikita Khrushchev, realised that the new American reconnaissance satellites had exposed his claim to possess a large Inter Continental Ballistic Missile force as a mere bluff. Feeling embarrassed and vulnerable, he took the gamble in 1962 of secretly deploying shorter-range missiles on the territory of his new ally, Cuba, in order to put American cities within range of a substantial Soviet missile force and thus close the strategic gap.

The US discovered the missiles, and the Cuban Missile Crisis erupted. The United States declared a blockade of Cuba, and began preparations for an invasion if Khrushchev didn’t withdraw his missiles. And faced with a real crisis, nobody paid the least attention to the idea of a “counterforce” or limited nuclear war.

The Soviet side was much weaker, but at least a few of Khrushchev’s bombers and missiles would get through to devastate American cities no matter what the United States did. Instead, everybody fled back to the relative sanity of Brodie’s original deterrent formula. On October 22, Kennedy declared that the United States would regard “any nuclear missile launched from Cuba against any nation in the Western Hemisphere as an attack by the Soviet Union on the United States requiring a full retaliatory response upon the Soviet Union.”

But there was still some time left, President Kennedy believed, for American intelligence sources were telling him that the Soviet missiles in Cuba still lacked their nuclear warheads. Kennedy therefore concentrated on intercepting Soviet ships that might be carrying the warheads to Cuba, while pushing ahead with the plan to invade the island if Moscow did not back down. And after a terrifying thirteen days, Moscow did back down. Khrushchev sent a letter to Kennedy offering to withdraw the Soviet missiles from Cuba in return for an American promise not to invade the island and to withdraw similar American missiles from Turkey a few months later. Nobody on the American side realised at the time just how close they had come to a nuclear war. If Khrushchev had not sent his proposal for a compromise, the US invasion of Cuba would probably have gone ahead, but everybody in Washington assumed that there would be at least a few more steps in the dance before nuclear weapons were actually used. 30 years later, Robert McNamara found out that everybody in Washington had been dead wrong.

It wasn’t until January, 1992, in a meeting chaired by Fidel Castro in Havana, Cuba, that I learned that 162 nuclear warheads including 90 tactical warheads were on the island at this critical moment of the crisis. I couldn’t believe what I was hearing, and... I said, “... Mr President [Castro], I have three questions to you. Number one, did you know the nuclear warheads were there? Number two, if you did, would you have recommended to Khrushchev in the face of a US attack that he use them? Number three, if he used them, what would have happened to Cuba?” He said, “Number one, I knew they were there. Number two... I did recommend to Khrushchev that they be used. Number three, what would have happened to Cuba? It would have been totally destroyed.” That’s how close we were... and he went on to say, “Mr McNamara, if you and President Kennedy had been in a similar situation, that’s what you would have done.” I said, “Mr President, I hope to God we would not have done it. Pull the temple down on our own heads? My God!”

— Robert McNamara, from 'The Fog of War'.

Threatening to pull the temple down on your own head and everybody else’s is the very essence of nuclear deterrence, but there is a measure of reassurance to be had from these events. The Cuban crisis demonstrated that the penalties for miscalculation in a nuclear confrontation are so huge that political leaders become extremely cautious and conservative in their actions; people do recognise the difference between simulation and reality. On the other hand, it also demonstrated that intelligence will always be imperfect and that seemingly rational decisions may actually be fatal.

If the United States had invaded Cuba to deal with the missiles before they were operational (as it thought), its Marines would have been obliterated on the beaches by tactical nuclear missiles launched by local Soviet commanders who had been pre-authorised to act without reference back to Moscow, and World War III would have begun. President Kennedy later estimated that the chance of the Cuban crisis ending in a nuclear war was one in three.

The Cuban Missile Crisis ought to have ended for good the notion of a limited nuclear war in American strategic circles: nobody seriously considered “signalling their resolve” with a few selective nuclear strikes when they were immersed in a real crisis. Nevertheless, the next twenty years of American nuclear war policy were largely dominated by the continuing split between the believers who wanted to make nuclear weapons usable in limited wars and those who had finally lost faith.

Excerpted with permission from The Shortest History of War, Gwynne Dyer, Pan MacMillan India.