There is one simple reason for this: 1989. This was the year of the end of Eastern Europe, the conclusion of the Cold War and the effective collapse of Communism. It was the year that brought the 20th century to a premature close. The Vietnam war was a child of Communism and the Cold War. The United States allowed itself to become mired in a hopeless conflict because it saw the war against the Vietcong as a matter of holding the line against the advance of Communism in Asia. The generation that mobilised against the war in the West perceived the Americans to be overwhelming and overweening aggressors. The conflict was articulated in terms of imperialism and national liberation, left and right. Vietnam was a creature of its time.
As such it is inconceivable that it could be staged now. The US is no longer seen in the same light. Where once its intervention anywhere in the world (from Asia to Latin America, the Middle East to Africa) was regarded with suspicion by many, today that intervention is often actively and consensually sought, Bosnia being the classic case in point. And in a period that has seen the discrediting of Communism, and complex wars such as those in the former Yugoslavia and Africa, it is difficult to imagine a generation again becoming so fiercely partisan in support of a left-wing guerrilla army in a backward country.
If the US is now overwhelmingly seen as a force for good, if we want it to intervene more rather than less, if guerilla insurgency is tarnished by its association with Communism, and if in the light of subsequent history the solidarity movement in the West seems extraordinarily innocent, even nave, were all the protests a waste of time, space and energy? It would not be an unreasonable conclusion.
But it would be wrong. Just because the West's struggle against Communism has been historically vindicated, it does not mean everything that was done in its name was right. The American war in Vietnam was wrong not only because it was ill-conceived and ended in ignominious failure, but above all because it so evidently represented an attempt to crush the national will of the Vietnamese people.
That was why the war turned into such an extraordinary conflict between the most powerful nation on earth, armed to the teeth with the latest technology, and a poor Third World country whose only weapons were its determination, pride and organisation. America's defeat in Vietnam drew a new line in the sand as to what was acceptable and unacceptable in the conduct of a superpower in the Third World. The end could not justify the means.
In the US itself, the impact of the Vietnam war has been profound. The memory of the returning body bags precluded any subsequent American military involvement elsewhere in the world, which risked serious loss of life. As happened earlier with Britain and France, Vietnam proved the high watermark of America's attempts to impose its will by force on other parts of the world. And the pain and anguish of the war and the subsequent defeat have barely diminished 20 years on, as the present debate there over the former Defence Secretary Robert McNamara's book illustrates.
If the historical line that links the Vietnamese war with today seems faint in the West, it is even more obscure in Asia. No continent was more scarred by the ravages of the Cold War than Asia: the biggest wars of that era were fought on its territory, Vietnam the biggest of them all, but also Korea, Cambodia, Laos, Malaya and many others. Only Europe was more visibly divided by the Cold War than Asia.
Yet today, the Cold War there, too, seems a distant memory. Indeed, even before America's defeat in Vietnam, a new chapter in the history of East Asia was being opened. For the economic rise of the four Asian tigers - South Korea, Taiwan, Hong Kong and Singapore - dates from around the early Seventies.
The discourse of the Vietnamese war was that of national liberation, anti-imperialism and socialism. The Asian tigers ushered in a completely different era, of rapid economic growth, the market, the creation of a new middle class, and booming prosperity. If Asia had been one of the defining continents of the Cold War, before that war's end, it began to prefigure one of the crucial new fault-lines of the post-Cold War era, the shift in the global centre of economic power from the Atlantic to the Pacific, from Europe to East Asia.
If Vietnam somehow became synonymous with Asia during the Cold War, at least in the minds of many Westerners,today we think rather of those countries - China and Malaysia, South Korea and Japan, Taiwan and Singapore, Hong Kong and Indonesia, Thailand and the Philippines - that are sharing in the mercurial economic growth of the region. While the Vietnamese conflict bore testimony to the importance of ideology and military prowess, today everything in almost every Asian country has been reduced to a matter of economics. Like much of western Europe in the Fifties, not least our own country, Asians have become obsessed with material things and making money.
Nothing attests more strongly to this new verity than the fact that Vietnam itself has become a late participant in Asia's economic miracle. It may still be ruled by the Communist Party but, as in the case of China, pragmatism in the cause of economic growth reigns supreme. Vietnam, too, has caught the capitalist bug.
So did the Vietnamese war mean little in Asia also? After all, the subsequent history of Asia has hardly been painted in the colours of the victorious Vietcong and its northern ally. Their ideology proved to have little endurance, as borne out by the extraordinary turn towards capitalism now signalled in Hanoi.
Yet in another, broader sense the Vietnamese war not only heralded the end of an era but also the start of a new one. Iteffectively drew the curtain on the long history of colonialism and against western intervention in Asia. It thereby helped to usher in a phase of self-confidence and self-respect for a continent that had suffered a long, bitter history of colonialism. The end of the Vietnamese war heralded, along with the rise of the Asian tigers, the Asianisation of Asia and the beginning of an era in which Asia is set to occupy a quite new position in the global order.
Photomontage: Michael Scorer