THE DOMINO THEORY
We were told, when the United States took over the debacle that the French had made of Southeast Asia, that we had to fight in Vietnam (and it turned out, in Laos and Cambodia) because if we did not defeat the dreaded "communism" in Vietnam (and it turned out, in Laos and Cambodia) the entirety of the rest of Southeast Asia would fall to the dreaded "communism" like so many dominos.
So we fought and sacrificed the lives of over 58,000 Americans and many times that number of Vietnamese (and it turns out, Laotians and Cambodians) and in the end, the dreaded "communists" won.
And did the prophesy of the "dominos" falling come true? Not even close to true. Now we look at China (the alleged sponsor of the dreaded "communists") and Vietnam (and it turns out Laos and Cambodia) and everywhere we look we see "capitalism" not "communism."