IN THE JAWS OF HISTORY By Bui Diem with David Chanoff Houghton Mifflin. 367 pp. $18.95

THE TITLE of this book really should be "How a big power treated a little client country so cavalierly and, in the end, so brutally, or least that's the way I feel about it and here's my life story as evidence." If you wonder what the United States is doing today in Nicaragua or the Persian Gulf or somewhere else, you'll find this book both intriguing and troubling. For the longtime clash between American idealism and American geopolitics has had, and still has, general application far beyond Vietnam, no matter what administration is in power in Washington.

The voice of authenticity is here; this is a proud man, an honest man now at long last telling us his story, not just Vietnam's. He is Bui Diem, descended from three generations of mandarins under French colonial rule, a person who preferred the backstage to the footlights and one who yearned for national freedom from autocratic rulers, domestic as well as foreigners (Chinese, French, Japanese, Americans). Yet he ended up flying his 90-year-old mother and sister to American exile just before the fall of Saigon to the armed ideologues of the North. Diem was chief of staff to the prime minister when Lyndon Johnson landed the Marines in 1965, South Vietnam's ambassador to Washington 1967-72 and finally envoy-at-large until 1975. As a reporter I dealt with him in those ambassadorial years and thought him a man of honor. He has proved it here.

The literature on the two Indochina wars, involving first France and then the United States, is ever growing and now there's a rash of films. But never before has a non-communist insider who played important roles for the various South Vietnamese regimes told us what this author does.

In the telling there is much mutual castigation: "The South Vietnamese people, and especially the . . . leaders, myself among them, bear the ultimate responsibility . . . and to be honest, they have much to regret and much to be ashamed of." Following "the obduracy of France" and the "ideological obession of Vietnam's Communists" came the "massive intervention by the United States, inserting into our struggle for independence and freedom its own overpowering dynamic." And: "The disastrous mistakes that were made were mistakes in implementation rather than intention. But the thrust of the policy of containment and protection, that I do not think can be faulted. It is, on the contrary, something for Americans to be proud of."

But the wordage of such generalizations, true as they may be to the author's thoughts, sounds more like the words of his co-author, David Chanoff. The real center of this book is Diem's account of his own life, from high school in Hanoi where in 1939 his French history teacher was Vo Nguyen Giap, later the communists' military genius. Giap's library contained Das Kapital in French and his student was urged to read it, and more. But Diem, though rejecting his father's mandarin "aloofness from the transitory things of this world," was swept up in the hopes that World War II would bring independence from France. His first sight of American power was a P-38 fighter attacking a Japanese camp near Hanoi; his first political act was to join the Dai Viet, an amalgam of democratically-minded, though often naive, nationalists in contrast to Ho Chi Minh's regimented communists.

World War II did end French, then Japanese occupation, but the French returned. They used the native Emperor Bao Dai who named Diem's uncle a prime minister and so the youngster began to learn practical politics. But Ho had proclaimed independence in Hanoi and soon the "fratricidal war between Communist and non-Communists bore down on us."

Just before the 1954 division of Vietnam by the great powers, after which American influence succeeded French in South Vietnam, Diem was serving in his uncle's defense ministry. American envoy Donald Heath told them that while the United States favored full independence from France, America remained a "multifaceted" ally of the colonial power. Thus Diem saw that "life and death issues for us were merely bargaining chips in the American pursuit of their global policy. This was a surprising lesson . . ., primarily because we had made an inordinate investment in what we understood as the idealistic thrust of American foreign affairs. It was a lesson we would relearn at far greater cost later on."

SOUTH Vietnam's acquiescence in the 1965 landing of U.S. Marines -- "an appalling picture" -- is the classical case of power and impotence. To Diem it seemed that the United States had "decided to fight a major land war in Asia" although back home Johnson denied any such idea and all but a few accepted his assurances. But soon the American "take charge" attitude, involving "enthusiasm and eagerness," "sometimes became overbearing." Defense Secretary Robert McNamara's "abrasive" demand to know, after the coup that eliminated Ngo Dinh Diem, "who's the boss here?" epitomized to Bui Diem the nature of the new colonialism.

LBJ, whom the ambassador saw frequently, is portrayed sympathetically; the Senate doves are treated with scorn. There are well-etched portraits of American ambassadors Heath, Maxwell Taylor, Henry Cabot Lodge, Ellsworth Bunker and Graham Martin and such other Americans as William Bundy, William Sullivan, Philip Habib and U. Alexis Johnson. Most particularly, however, it is Diem's extensive dealings with, and descriptions of, the leading South Vietnamese players that stand out. Although tagged Nguyen Cao Ky's man, he managed to work with the more powerful and dictatorial Nguyen Van Thieu. It was he who was the great procrastinator in dealing with the Americans. The Americans, "in finding their way out of the war," did not deviate from the peculiar arrogance with which they found their way in and with which they afterwards conducted it." To Diem there was an "institutionalized American moral failure . . . complemented on the South Vietnamese side by an abject failure of leadership, passive and dilatory and incapable of assuming the burden of responsibility for the nation."

Personalities counted. Henry Kissinger did Richard Nixon's dirty work to end it for Americans, using the rubric of flexibility. How could it be otherwise? Diem had come to trust Republican Senators George Aiken, Everett Dirksen and, later, John Tower. The Saturday after Nixon's election, Dirksen came alone to the ambassador's door (soon to be followed by journalist Joseph Alsop) to deliver LBJ's message that the "two presidents" demanded that Thieu join the Paris peace talks "before it's too late." Diem also describes the 1968 election eve maneuvers involving Anna Chennault, which some saw as designed to defeat Hubert Humphrey. The tale fascinates but key parts remain missing.

It was an American-Vietnamese "ill-fated symbiosis," Diem writes. And probably this is the best evidence yet of why.

Chalmers M. Roberts is the former chief diplomatic reporter for The Washington Post.