WHEN I was a university student during the Vietnam War we had long debates about the domino theory that if South Vietnam fell then the rest of Indochina and, one by one, the remaining countries of southeast Asia, would go communist in rapid succession.
It was, as some of us who supported it were told loftily, a theory quite unproven and discounted by many experts.
In the event, it seemed largely borne out by what happened in 1975, if not exactly in the neat and tidy way that some predicted: Cambodia and Laos fell as, and plainly because, Saigon fell.
The other southeast Asian countries, which had been given time to strengthen their economies and political institutions by the long holding action in Vietnam, did not fall. The bottle stayed corked, as The Economist put it.
However, emboldened by this wave of victory, communist movements with Soviet help staged takeovers in a series of other, not geographically contiguous, countries, with communist or far-leftist regimes coming to power in Benin, Ethiopia, Guinea-Bissau, Madagascar, Cape Verde, Mozambique, Angola, Afghanistan, Grenada and Nicaragua during the 1970s.
The last domino to fall was probably the Smith regime in Rhodesia in 1980: the Marxist takeovers in neighbouring Mozambique and Angola had made its position hopeless.
There was an upsurge of revolutionary communist and leftist movements in western Europe and the US at about the same time - including groups such as the Red Brigades, the Baader-Meinhof gang, and the Weather Underground.
A few years later, and perhaps partly in reaction, we saw the dominoes falling again, but this time they went the other way. Possibly the costly Soviet failure in Afghanistan was the first signal that the Red Army, which we had been told would be able to sweep NATO forces into the Atlantic in a few days in the event of a general attack westward into Europe, could not even subdue a poor, backward nation with which it shared a border. Read more.