VIETNAMESE OF my generation came of age in the early 1940s with the hope that after almost a century as second-class citizens in their own country, they would have a chance to recover their dignity and achieve their independence from France. They dreamed also of peace and a decent life for themselves and their children. It was their misfortune that instead of independence, peace, and a decent life, they saw only revolution, war, and destruction. For three decades they existed in the maelstrom. And even now, when Vietnam no longer has to deal with foreign invaders, their misery continues.

The South Vietnamese people, and especially the South Vietnamese leaders, myself among them, bear the ultimate responsibility for the fate of their nation, and to be honest, they have much to regret and much to be ashamed of. But it is also true that the war's cast of characters operated a matrix of larger forces that stood outside the common human inadequacies and failings. And it was these forces that shaped the landscape on which we all moved.

As I look back on the external forces that shaped our lives, it is the American intervention that stands out. French colonialism, after all, is dead and gone, a subject of historians who prefer the inert remains of the past to the passions of the present. As for Vietnamese communism, no one but the fervid or the blind any longer argues the merits of a system that has brought in its wake only war and deprivation and mass flight. But American intervention is a living issue. In the train of failure in Vietnam, and in the face of hard choices elsewhere, the questions of its correctness and its morality still inform American foreign policy debates. Americans still seek to learn the lessons of intervention, and so do America's smaller allies, who cannot help but see in the fate of Vietnam intimations of their own possible futures.

To my mind, the lessons of American intervention in Vietnam have to do not so much with the geopolitical or moral underpinning of the war, but rather with the way the intervention was implemented. The real question was not whether to intervene, but how to intervene effectively.

The salient feature of America's confused and unclear process of intervention (as Bill Bundy characterized it) was the startling attitude of American decision makers toward their ally. At the top levels of the administration, there is no evidence that anyone considered the South Vietnamese as partners in the venture to save South Vietnam. In a mood that seemed mixed of idealism and naivete, impatience and overconfidence, the Americans simply came in and took over. The message seemed to be that this was an American war, and the best thing the South Vietnamese could do was to keep from rocking the boat and let the Americans get on with their business.

The military consequences of this orientation were that the United States took the entire burden on itself instead of searching for ways to make a decisive impact while limiting its exposure. Had the South Vietnamese been consulted in early 1965, it is likely they would have preferred either no intervention or a limited effort sufficient to stabilize the military situation and block the infliteration routes from North Vietnam. An agreement among the United States, South States, South Vietnam, and Laos, allowing U.S. troops to be stationed along the seventeenth parallel as a barrier, would have been quite feasible at the time. With that done, an immediate Vietamization program could have been undertaken to strength and upgrade the South Vietnamese army.

On the political level, too, this American failure to regard the South Vietnamese as people worthy of partnership had destructive results. It meant that the United States never pursued a consistent policy aimed at encouraging the development of a viable democracy in South Vietnam. Certainly, such a thing was possible. Between 1965 and 1967 the South Vietnamese drafted and adopted a constitution, elected a president, vice president, and legislature, and successfully held many local elections -- all of this in the middle of a war.

Unfortunately, thereafter "stability" became the American watchword. As long as the Saigon government demonstrated a modicum of equilibrium, that was all that was asked of it. Several years of progress toward decent government might erode, corruption and autocracy might swell, but these things were not a primary American concern. By 1969 Henry Kissinger and Richard Nixon had embarked on a complex chess game, manipulating big-power diplomacy, military force, and secret negotiations in an attempt to extricate the United States from its quagmire. Amidst this constellation of variables, they needed a government in Saigon that was stable and predictable. If Thieu gave them that, then whatever else he might do was essentially irrelevant.

It was a fatal error on two counts, First, stigmatized as undemocratic and corrupt, South Vietnam was deemed unworthy of support by an ever-increasing percentage of the American public and Congress. Second, within South Vietnam, the unpopular nature of the regime produced apathy, cynicism and finally, in the anticorruption movement, outrage. Admittedly, bringing pressure for reform and democracy is a delicate business. But where the United States has significant leverage, the role of catalyst for change, of prodding contending factions toward consensus, beckons to American diplomacy.

To successfully play such a role, there are two prerequisites. One is the will to carry out a strong and consistent advocacy. The other is the determination to accept the consequences if in the end American pressure proves unavailing. The United States must find a way to say to a Ngo Dinh Diem or a Nguyen Van Thieu (or a Ferdinand Marcos or an Augusto Pinochet): "We have no alternative but to stand by our own values. If for your own reasons you find you cannot bring yourselves toward conforming with them, then we are very sorry, but we will have no choice but to leave you to your own devices." With all its power and prestige, the United States simply cannot allow itself to yield to the tyrranny of the weak, to authoritarians who believe their importance is so vast that the United States cannot help but support them. If Vietnam has one lesson to teach, it is that people cannot be saved in spite of themselves. Far better to get out and cut losses before ensnaring treasure, lives and prestige in the service of those whose rule means violent discord and social breakdown.

Of all the successive phases of U.S. involvement -- the intervention of 1965, the Americanization of the war, then its Vietnamization, and finally the disengagement -- it is the disengagement that will stick longest in the minds of the South Vietnamese. Major mistakes were made during the war by everyone concerned. But the manner in which the United States took its leave was more than a mistake; it was an act unworthy of a great power, one that I believe will be remembered long after such unfortunate misconceptions as the search and destroy strategy have been consigned to footnotes.

It was not that leave-taking itself was a disgrace. The United States fought long and hard in Vietnam, and if in the end circumstances required that they withdraw, it may be considered a tragedy but hardly an act of shame. The same cannot be said, however, for the manipulative and callous manner with which the American administration and the American Congress dealt with South Vietnam during the last years of the war. It was not one of America's finest hours, and there are plenty of lessons in it for both the United States and for other nations, particularly small ones that must rely on the United States for their defense.

"Is it possible for a great nation to behave this way?" That was the question an old friend of mine asked me in Saigon when news came in August of 1974 that Congress had reduced the volume of aid. He was a store owner with whom I had gone to school in North Vietnam, a totally nonpolitical person. "You are an ambassador," he said. "Perhaps you understand these things better than I do. But can you explain this attitude of the Americans? When they wanted to come, they came. And when they want to leave, they leave. It's as if a neighbor came over and made a shambles of your house, then suddenly decides the whole thing is wrong and calls it quits. How can they just do that?" It was a naive question from an unsophisticated man. But I had no answer. Neither, I think, would William Fulbright or George McGovern or other antiwar congressmen.

In the end, though, the culpability is hardly theirs alone. So many thought they knew the truth. The newsmen -- as arrogant as any -- Kissinger, Thieu, Nixon, myself as well. But none of us knew the truth or, knowing it, took it sufficiently to heart. Not we, and certainly not the implacable and ruthless ideologues who were our enemies. The truth is in the millions of Vietnamese families that have suffered the most horrible tragedies, people who understood what was happening only in the vaguest way. The truth of this war lies buried with its victims, with those who did, and with those who are consigned to live in an oppressed silence, for now and for the coming generations -- a silence the world calls peace.

Bui Diem was South Vietnam's ambassador to Washington from 1967 to 1972. This article is adapted from his new book, "In the Jaws of History," written in collaboration with David Chanoff.