Historians often casually refer to the “discredited” Domino Theory.  For example, the History Channel website tells us:

The domino theory was a Cold War policy that suggested a communist government in one nation would quickly lead to communist takeovers in neighboring states, each falling like a perfectly aligned row of dominos. In Southeast Asia, the U.S. government used the now-discredited domino theory to justify its involvement in the Vietnam War and its support for a non-communist dictator in South Vietnam. In fact, the American failure to prevent a communist victory in Vietnam had much less of an impact than had been assumed by proponents of the domino theory. With the exception of Laos and Cambodia, communism failed to spread throughout Southeast Asia.

But how much did historical fact actually “discredit” the Domino Theory?  The obvious hurdle is the vagueness of the theory.  Here’s Eisenhower’s original 1954 statement about Indochina:

Finally, you have broader considerations that might follow what you would call the ‘falling domino’ principle. You have a row of dominoes set up, you knock over the first one, and what will happen to the last one is the certainty that it will go over very quickly. So you could have a beginning of a disintegration that would have the most profound influences.

The word “certainty” in the second sentence sounds strong, but the third sentence is weak tea indeed.  “You could have the beginning of a disintegration” could mean… almost anything.  Typical non-falsifiable political poetry.

What, though, would a numerate adherent of the Domino Theory have said in 1954?  Presumably he wouldn’t have huffed, “I’m only right if Vietnam goes Communist, then every other country in Asia goes Communist within a year.”  Instead, he would name a lower number and a longer time frame.  Probably something like 3-5 south-east Asian countries going Communist within 5-10 years.

So what actually happened?  Since Eisenhower was speaking just before the Geneva Accords split Vietnam in two, it would be fair to say that the rise of Communism in North Vietnam did indeed bring three more countries under Communist control: South Vietnam, Laos, and Cambodia.  It took a little over two decades, but once South Vietnam fell, the other two crumbled the same year.  Hardly a decisive confirmation for a testable version of the Domino Theory, but far from a crushing disconfirmation either.

On reflection, though, this analysis treats the Domino Theory unfairly.  Key point: If people in power correctly believe that the Domino Theory is true, the theory’s predictions become self-reversing.  Why?  Because leaders who believe the Domino Theory will struggle mightily to stop dominoes from falling – and reinforce dominoes in danger!

Picture an alternate history where American Domino Theorists successfully contain North Vietnam.  Zero neighboring countries go Communist in the next decade.  Critics would probably claim that the non-spread of Communism “discredits” the Domino Theory.  Domino Theorists could however fairly object, “Our leaders listened to us – and got the result we predicted if you listened to us.”

History definitely presents better examples of the Domino Theory at work that south-east Asian Communism.  Once the world saw that the Soviet Union was unlikely to militarily intervene, Communism crumbled in every Communist state in eastern Europe in less than a year (except, of course, for the USSR itself).  Now that’s a Domino Effect!  My claim is not that the Cold War Domino Theorists were clearly right, but simply that they were far from clearly wrong.  This is a classic case of, “If you’re not confused, you don’t understand what’s going on.”