In retrospect, it`s clear that the Communists were telling the truth. They won the war in Vietnam despite all the efforts of the United States, but the “domino effect” in the rest of South-East Asia never happened. In fact, the Vietnamese Communists never even tried to knock the dominoes over.
Apart from invading Cambodia in 1978 to drive the Khmer Rouge, a much nastier group of Communists, from power, Communist-ruled Vietnam has never sent troops abroad or interfered in the internal affairs of other countries in the region. After a decade all the Vietnamese troops were withdrawn from Cambodia, and even there Hanoi has virtually no influence today.
As for some vast Communist plot to overrun South-East Asia, it was never more than a fantasy. Indeed, within four years of uniting Vietnam, the Communist regime in Hanoi was at war with Communist China over a border dispute. In a perfect world, most people would probably prefer to spare their country the burden of a generation of Communist rule, but Vietnam is not a disaster, and it is no threat to anyone else.
So, once again, what was the war about? How did three American presidents allow themselves to be misled into fighting such a pointless, unwinnable war? Dwight Eisenhower, John Kennedy and Lyndon Johnson were all intelligent men, and Eisenhower also had much experience at the highest level of military and diplomatic decision-making.
To varying degrees, they all fell for a strategic vision of the world that was mere fantasy, driven by ideology. Or rather, in Eisenhower`s case and to some extent also in Kennedy`s, they found it politically impossible to resist the demands of those who did live fully within that fantasy. So American foreign policy had little connection with reality for several decades, and a lot of people died.
The point is that this sort of thing happens all the time. The “war on terror” now is functionally almost indistinguishable from the anti-Communist crusade of the 1950s and 1960s, although the actual wars involve much lower levels of casualties. For Vietnam in 1960, read Iraq in 2003.
It doesn`t only happen to Americans, of course. The various British invasions of Afghanistan in the 19th century were driven by the conviction that the rapacious Russians wanted to seize Britain`s Indian empire, although the thought hadn`t even occurred to the Russians. Germans spent the decade before the First World War worried that they were being “encircled” by the other great powers.