ON THE MORNING of April 30, 1975, as Saigon fell to our forces, I was with the first tank unit to crash through the gates of the presidential palace in the South Vietnamese capital. Though I was then serving as a correspondent for our army newspaper, I was the senior officer present, and my comrades insisted that I accept the surrender from General Duong Van "Big" Minh, the last head of the defeated Saigon government. I had fought for more than 30 years, first against France and later against the United States, and I was both relieved and elated by our triumph. Now, I felt, our divided nation could finally be reunifed in peace and independence. Inviting our former enemies to join us in the task of reconstruction, I sought to calm their anxieties. "Between Vietnamese there are no victors and no vanquished," I said. "Only the Americans have been beaten. If you are patriots, consider this a moment of joy."

But that joyful moment has long since turned sour. Over the past 16 years, the Communist rulers have failed to bring liberty and prosperity to Vietnam. Rather than improve the abysmal condition of the population, they have blindly pursued sectarian policies designed to maintain their power. As a consequence, Vietnam remains one of the poorest lands on earth -- a fact reflected in the massive exodus of "boat people," who have courted terrible risks in their efforts to escape relentless misery.

The tragic irony of this situation is that the Communists have finished what America's military machine only partly did during the war. They have crushed Vietnam, thereby squandering the achievement for which a million of our troops and countless numbers of civilians sacrificed their lives.

Communism has been rejected in the Soviet Union and nearly everywhere else in the world. But the Communist leaders in Hanoi, fearful for their authority, continue to resist that trend and have become increasingly dogmatic, intransigent and repressive. At a recent party congress, for example, they expressed their determination to "go forward down the path of socialism," vaunting it as "the superior system for humankind." They still proclaim such dogmatic Marxist-Leninist tenets as the "dictatorship of the proletariat" and "democratic centralism" as a device to assure their control. Their spokesmen constantly warn against "imperialist reactionary" plots aimed at sabotaging the regime, using that tactic to jail dissident writers and other intellectuals and expel foreigners who went to Vietnam to assist the country. These acts mirror their confusion, perhaps even panic, as global communism crumbles, leaving them isolated except for a new and uneasy accommodation with China, a neighbor they distrust.

Though many Westerners have spoken approvingly of Doi Moi, the Vietnamese Communist reform program, its impact has only been superficial. It has spawned bars, nightclubs, prostitution and pornography, but nothing has been done to promote free elections, free speech and a free press. Similarly, an investment law passed in 1986, often hailed as one of the most liberal in Asia, exists more on paper than in reality. And it is likely to remain academic as long as the Communist structure nurtures an entrenched, corrupt and inefficient bureaucracy. A true market economy of the kind that attracts foreign business cannot function under an authoritarian regime chiefly dedicated to its own survival.

Nor is the Communist Party as secure as it looks from abroad. It is tough enough to check opposition, but its strength may be deceptive. Some 200,000 Vietnamese workers are now returning home from Eastern Europe, where they have witnessed the collapse of communism, and they may clamor for change. As a professional officer, I know that disaffection is widespread both inside the army and among discharged soldiers, thousands of whom cannot find jobs in the stagnant economy. Just before their congress last June, the party leaders retired hundreds of generals and colonels whom they suspected as a threat to their power. To predict an upheaval in Hanoi of the kind that roiled Moscow may be rash, yet it would be equally illusory to ignore Vietnam's potential instability.

In 1945, at the age of 18, I was motivated by nationalism rather than ideology to rally to the Vietminh, the movement organized by Ho Chi Minh to fight France's colonial rule in Vietnam. From then on, war was my life. I was wounded in 1954 at the famous battle of Dienbienphu, where we routed the French, and I later conducted several important missions in the struggle against the Americans, such as planning the secret deployment of northern troops into the south in 1964. Afterward I served as deputy editor-in-chief of Quan Doi Nhan Dan, the army newspaper, and eventually became deputy editor-in-chief of Nhan Dan, the official Communist journal.

Throughout those years I was close to Ho, who died in 1969. I was also close to his successors, and I observed how they betrayed his principles following the war.

They would evoke Ho's celebrated slogan, "Nothing is more precious than independence and freedom." But to justify their repression, they deliberately ignored the rest of his dictum, "Independence without freedom is worse than no independence."

Their blunders were monumental. When the American combat troops departed Vietnam early in 1973, for instance, they abandoned vehicles, aircraft, ships and other materiel worth billions. This equipment, which later fell into our hands, could have contributed to the recovery of the country, but it was gradually stolen by cadres, traded on the black market or left to rot. When the Communists took over the south, they seized 16 tons of gold belonging to the Saigon regime. A former Saigon government official, versed in financial matters, recommended that it be converted into dollars and deposited in foreign banks so that the interest would yield a hefty sum in desperately scarce hard currency. But Truong Chinh, then the party boss, snubbed the idea on the grounds that "we do not deal with capitalists." A few years later, when I asked him what had happened to the gold, he admitted that "we have spent it little by little and now it is almost gone." {See story above.}

I repeatedly cautioned the Communist leaders against introducing rigorous collectivization programs into the south, pointing out that its people, who were accustomed to free enterprise, would become demoralized. My counsel was ignored, and peasants were forced into big state farms ceased to produce. Having personally invited Big Minh and his aides to join in healing the wounds of war, I also advised against shunting hundreds of thousands of southern officials and army officers into so-called "re-education camps." Again I was spurned, and our government lost an enormous reservoir of talent.

I accompanied the first wave of Vietnamese troops to invade Cambodia at the end of 1978, and I believe that our action was justified as a riposte to Khmer Rouge incursions into our territory from Cambodia. But after driving the Khmer Rouge out of Phnom Penh and effectively dispersing their force, we should have offered to withdraw from Cambodia and turn the problem over to an international body. I was rejected when I proposed this approach to our leaders. They further asserted that Cambodia belonged to an Indochina community, presumably under Hanoi's auspices. The result of their strategy was to isolate Vietnam further from the rest of the world -- in particular, to set back hopes for a rapprochement with the United States.

These rebuffs notwithstanding, I stayed with the party. I was persuaded that I could work privately and quietly from the inside, along with others who shared my concerns, to convince our leaders of the need for sweeping reforms. I was mistaken. The Communist party, obsessed with defending itself, refuses to respect differences, and its apparatus will exterminate anyone and extinguish any voice that challenges its purpose. With the party making the rules, there can be no competition between policy choices that enable the people to decide on the best course. Only genuine democracy promises that approach. Ultimately I realized that it was futile for me to attempt to publicize my views to the Vietnamese people from Hanoi, and I conceived the idea of broadcasting my opinions back to Vietnam from abroad. My chance came late last year when I was sent on an official mission to Paris. I obtained permission to prolong my visit there, ostensibly for medical treatment. From there I made a series of weekly broadcasts to Vietnam over the Vietnamese-language services of the British Broadcasting Corp. and other foreign media. Calling my commentaries the "proposals of a citizen," I studiously avoided criticizing the Vietnamese leaders by name. Instead I appealed for political pluralism and a rational economic agenda based on Ho Chi Minh's policy of national unity and conciliation.

I had no intention of defecting and indeed hoped to return to Hanoi to carry on my campaign. But friends told me that it would be unsafe to do so after I was denounced as a "traitor" and stripped of my Communist Party membership.

Nevertheless, I was successful. Millions of Vietnamese, including many of my former Communist Party comrades, have heard and esteemed my words. Tapes of my broadcasts, I have learned, continue to circulate surreptitiously in Vietnam.

As events in the Soviet Union and Eastern Europe demonstrated, reformers within the parties there understood that the more stubbornly the party defies change, the more chaotic and violent the change would be when it occurs. So, despite my ouster, I am not implacably hostile to the Vietnamese Communist Party, which also contains a small yet determined number of honest, far-sighted members who appreciate the necessity for genuine renovation. But where Vietnam is headed at this stage is far from clear.

In a compromise move, the party congress held in Hanoi last spring dumped both Mao Chi Tho, the hard-line minister of interior and Nguyen Co Thach, the liberal foreign minister. The new prime minister, Vo Van Kiet, is reputedly open-minded but hardly a forceful figure. The party is thus run by its cadres, most of them badly educated, unskilled and venal, whose principal objective is to cling to their jobs. Hence the prospects for full-scale renovation seem slim.

In restrospect, it breaks my heart to think of those on our side who suffered for an empty victory. Not only do I lament the deaths of my country's youth, but I regret my own wasted energies during those terrible years of war. I also grieve for the Vietnamese Communist Party, which under Ho's banner once symbolized the struggle against colonialism and is now defiled. And I mourn Vietnam's fall from the vanguard of global revolution to a bastion of discredited doctrines.

But the possibility of a relationship between the United States and Vietnam promises hope, since U.S. aid, trade, culture, science and technology can play a decisive role in support of the Vietnamese liberals who strive through democracy to lift their nation out of poverty and repression caused by Communist rule. Hence my message to Americans, whether they were past hawks or doves: Do not forget Vietnam, where a population of 70 million puts its faith in you, now more than ever. Sixteen years ago you lost the war. Today you have an opportunity to help win the peace and gain the friendship and gratitiude of the entire Vietnamese people, who desperately seek to rejoin the world.

Bui Tin, reserve colonel in the Vietnamese army and former deputy editor-in-chief of Nhan Dan, the Vietnamese Communist Party newspaper, left Vietnam last year and is writing a book about his experiences.