From this day on, generations of Americans will come upon the black granite memorial to the veterans of Vietnam on the greensward of the Washington Mall and find there, first in the ranks of the dead, the names of Dale Buis and Chester Ovnard.

At dusk, on July 8, 1959, they sat down in a small mess hall 20 miles north of Saigon to watch a Jeanne Crain movie, "The Tattered Dress." Buis, an Army major from Imperial Beach, Calif., had been in that sliver of a country in Southeast Asia only two days on assignment as a military adviser. Ovnard, a master sergeant from Copperas Cove, Tex., had been around longer. That day he had mailed off a letter to his wife telling of his experience there.

As the lights dimmed, peasant guerrillas crept from the shadows to the mess hall windows. A few minutes later they opened fire. Buis and Ovnard were dead when they fell to the floor. They were the first American casualties of what was to become America's war in Vietnam.

The U.S. involvement in that distant place had begun nine years earlier with a decision by America's 33rd president, Harry S Truman, to provide military assistance to the French.

Now, in the way of all wars, it enters a more permanent page of history with the consecration of a memorial this week in Washington so that those who fought and died will not be forgotten.

The memorial, set in the most peaceful of places in the graceful quiet park along the banks of the Potomac, stands surrounded by other symbols of the American past and present: the white shrine of the brooding Lincoln, the towering marble of the Washington Monument, the great dome of the Capitol rising above the city. Each of them carries a clear national message, whether of celebration of the country's founder in its war of independence, or of its savior in its war of rebellion, or of its continuing experiment of democratic governance in the halls of Congress.

Alone among them all, the Vietnam memorial fails to convey an undiluted message. It merely lists the names of the57,939 Americans who died during the long years of the war in Vietnam. Why they fought there, who sent them, and for what purpose are questions unanswered as they are unraised. Not even a Lincolnesque pledge about ensuring that these honored Americans shall not have died in vain, words that you will find carved on the walls of his temple nearby and which have become customary in other war memorials, marks this spot.

That is fitting, for even today the meaning and lessons of Vietnam remain shrouded in ambiguity and enmeshed in controversy. It was unique among all American wars. One of many ironies is that we do not even agree on when it began or ended. Some would say the beginning was in 1950 when the first American military advisers were committed. The veterans who have built the memorial chose the date on which Buis and Ovnard died. Lawrence Baskir and William Strauss, whose seminal book, "Chance and Circumstance," defines the Vietnam "generation," date the beginning from 1964. As for the end of it, it could have been 1973 when the last combat units were withdrawn or it could have been 1975 when the American Embassy in Saigon finally was evacuated.

Whatever the time frame, it was at once the nation's longest and most divisive external conflict. From its slow, almost accidental beginnings more than three decades ago, it flared into the central trauma of a generation. Gradually but inexorably it drew unto itself the lives and talents and careers of millions of Americans. It became the preeminent national concern, a conflict that divided Americans against Americans, separated people along class lines into the ranks of those who served and those who didn't. It affected our politics (some would say poisoned it), altered some of our old perceptions about ourselves and our country, and raged at the center of American life for year after year. Six presidents grappled with it: Truman, Eisenhower, Kennedy, Johnson, Nixon, Ford. One, at least, Johnson, was destroyed by it. Their successors continue to react to it.

In the end it was the war we never won, and we never seemed to understand why we were there in the first place. Early on, in 1954, when George Gallup asked Americans what the country would gain from fighting in Indochina, a great plurality replied: "Nothing." Ten years later, a great plurality was anxious to get involved, although millions of Americans could not locate Vietnam on a map and paid little or no attention to what was happening there.

Today, although only seven years have passed since the last American helicopters flew off in a scene of mad desperation and humiliation from the fallen capital of Saigon, millions of younger Americans know even less what it was all about. All they have to ponder are memorials, and figures.

The statistics, compiled by Baskir and Strauss, do not unravel the mystery of how it was that a small, primitive, faraway land so consumed the lives and treasure of the world's greatest military and economic power.

But they are nonetheless revealing and eloquent so far as numbers or names on a wall can be said to be eloquent. At the minimum, they measure unequal sacrifice and danger, they reveal the chance and the circumstance of life in the Vietnam era and they speak to the diversity and polarization of that generation.

Of the 53 million Americans who were born between the years 1946 and 1953 and came of age between the dates Aug. 4, 1964, (when the congressional Gulf of Tonkin Resolution formally made Vietnam a United States conflict) and March 28, 1975 (the fall of Saigon), some 11,250,000 served in the military, all but 250,000 of them males. That leaves 42 million who did not serve -- roughly 80 percent of the entire "baby boom" generation, the Pepsi kids. Of the 42 million, roughly 26 million were women whose services were not demanded; 15.4 million were men who were deferred, exempted, disqualified or who evaded service.

Of the 11 million or so who wore military uniforms in that era, approximately 2.2 million were sent to Vietnam; 17,000 died of gunshot wounds, 7,500 from shrapnel, 6,750 from grenades and mines, 10,500 from other enemy actions, 8,000 from accidents and other "non-hostile" causes and 350 by suicide. Those are the names on the wall of the memorial. Another 270,000 were wounded, of whom 21,000 were disabled and 5,000 lost one or more limbs.

And what of those who by chance or circumstance did not serve? The vast majority were freed from service by the liberal selective service laws and rules. But a small percentage -- about 570,000 men -- were classified as "draft offenders." Of that number, about 200,000 were charged with offenses and a small fraction, 8,750, were convicted; 3,250 served brief prison terms; 30,000 fled the country or went underground. Cases against 198,000 accused offenders were dropped.

These impersonal rows of raw data form the human material of the tragedy that was Vietnam but only hint at the bitterness and turmoil they represented during a war that still haunts the country and still leaves issues and emotions unresolved.

It was begun, as Harry Truman said at the time, to prevent a "Communist takeover" of Southeast Asia. But it was also a colonialist undertaking against revolutionaries inspired by nationalistic passions. That dilemma continues today to confront the United States in dealings around the world. Which side do you choose?

Ho Chi Minh, the Vietnamese leader of the 1950s, had helped Americans during World War II by working closely with our Office of Strategic Services, the so-called OSS, the forerunner of the CIA. He also helped rescue downed American pilots. On V-J Day in 1945, the day marking the end of the second world war, Ho proclaimed the independence of all Vietnam from the French. From that moment he began leading the long, vicious war of liberation that cost the French 174,000 casualties, and after their great defeat in 1954 at Dienbienphu, their colony.

The United States moved to fill the vacuum of that French defeat, thus vastly expanding an initial commitment that had begun in the early months of the Korean War.

In August 1950, confronted with a Communist invasion from North Korea, and facing the peak of the Cold War era, it was easy for American policymakers to view the French fight against Asian Communists as analagous to the Korean conflict. It was equally easy to discount considerations of nationalism and anticolonialism.

So it was that the first 35 American military advisers, watched sullenly by the French, arrived in Vietnam that summer of 1950.

Over the years the U.S. commitment grew slowly but steadily. By Oct. 12, 1952, the 200th American ship carrying military aid had docked in Saigon. Two years later, at the time of Dienbienphu, with the new Eisenhower administration in power, the U.S. nearly intervened directly on behalf of the French. But the arguments of Gen. Matthew Ridgway, the hero of Korea and the U.S. Army chief of staff, prevailed during the policy debate in Washington.

"In Korea," he wrote two years later, "we had learned that air and naval power alone cannot win a war and that inadequate ground forces cannot win one either. It was incredible to me that we had forgotten that bitter lesson so soon--that we were on the verge of making that same tragic error. That error, thank God, was not repeated."

Out of those deliberations came a fateful policy declaration. At a press conference on April 7, 1954, Eisenhower was asked to comment on the strategic importance of Indochina to the free world. He promulgated what he termed "the falling-domino theory."

"You have a row of dominoes set up," he said, "you knock over the first one, and what will happen to the last one is a certainty that it will go over very quickly. So you could have the beginning of a disintegration that would have the most profound influences."

In Eisenhower's view, the loss of Indochina would be followed by Burma, Thailand, the Malay Peninsula, and Indonesia until "now you are talking about millions and millions of people." But it wouldn't stop there. The dominoes would continue to fall until Australia and New Zealand were threatened, until the defensive island chains of Japan, Taiwan and the Philippines were forced to turn toward the south, and until they had only one place to go -- to the Communist East.

Presidents and secretaries of state would come and go, years would pass, and the U.S. commitment would swell from hundreds into the hundreds of thousands and finally millions before that proposition was tested in the blood and jungles of Southeast Asia. By then, Americans came to share the earlier feelings of the French about Vietnam. To us, as to them, it was la guerre pourrie -- the rotten war, the most frustrating war, and, on its face, the most unlikely war for Americans.

The United States went into it willingly enough with broad public and political support in the early 1960s. The "establishment" newspapers -- The Washington Post and The New York Times, for example -- applauded and rationalized America's intervention to "save Vietnam." So did a generation of U.S. policymakers of all political and ideological persuasions. Like the country, they changed positions in the later 1960s as the costs and casualties mounted and the people asked, "To what end?"

A telling measure of shifting public attitudes was a question asked in an opinion poll of male high school students in 1966. What did they worry about? Only 7 percent mentioned the draft. By 1969, the draft worried 75 percent of them.

This was the time of the great antiwar demonstrations, the "days of rage" when it seemed governments might topple overnight. Those days and emotions here at home were extensively recorded. The "rage" that came later was the rage of the 3 percent of the Vietnam generation who had fought in the war, who were not given the political luxury of changing their minds and who came home to find themselves, in many cases, ignored at best, and at worst, regarded and treated as war criminals.

It is out of that rage, out of a desire for recognition and respect for what they had gone through, and out of their pride as soldiers that the Vietnam memorial was born. Not surprisingly, even that simple longing for national understanding brought with it controversies and anger over what the memorial should be and what the war had meant. The organizers of this week of reunion and dedication hope it will lead to the final reconciliation of a generation fractured by one of the most searing epochs of the American experience.