It was Mrs. Tuchman's fourth book, ''The Guns of August,'' a study of the background and beginning of World War I, that made her a celebrity after it came out in 1962, winning reviewers' salutes, a durable niche on best-seller lists and her first Pulitzer Prize.
The second Pulitzer came for ''Stilwell and the American Experience in China, 1911-45.'' The 1971 biography of Gen. Joseph W. Stilwell, a hard-driving American officer who played a major role in China during World War II, was combined with a history of modern China. Her other books included ''The Zimmermann Telegram,''''The Proud Tower'' and ''A Distant Mirror.'' Latest Book a Best Seller
Her most recent book, ''The First Salute,'' sets the American Revolution in international perspective. It has been on the New York Times best-seller list for 17 weeks, and last week was No. 9.
Born into a New York family that had long been eminent in finance and public service, Mrs. Tuchman could have had an easy, conventional life as the wife of a prominent physician. But as her three daughters grew older, she took up the historian's profession.
She had neither an academic title nor even a graduate degree. ''It's what saved me,'' she later said. ''If I had taken a doctoral degree, it would have stifled any writing capacity.''
Her Primary Obstacle
But to be a writer was difficult, she found, simply because she was a woman. ''If a man is a writer,'' she once said, ''everybody tiptoes around past the locked door of the breadwinner. But if you're an ordinary female housewife, people say, 'This is just something Barbara wanted to do; it's not professional.'''
In fact, Mrs. Tuchman had a firm, even contentious, sense of her vocation. In history and biography, she told an audience at the National Portrait Gallery in 1978, ''the writer's object is - or should be - to hold the reader's attention.''
''I want the reader to turn the page and keep on turning to the end,'' she added. ''This is accomplished only when the narrative moves steadily ahead, not when it comes to a weary standstill, overloaded with every item uncovered in the research.'' An Impression of Authority
In her person as well as in her choice of words, Mrs. Tuchman gave an impression of authority. She had strong features, a high forehead, wise hazel eyes and a somewhat serious manner that gave way, now and then, to a dazzling smile.
Summing up her view of the historical process, she wrote in 1981, in the preface to ''Practicing History,'' a selection of her short writings, that she had arrived at ''a sense of history as accidental and perhaps cyclical, of human conduct as a steady stream running through endless fields of changing circumstances, of good and bad always coexisting and inextricably mixed in periods as in people, of cross-currents and counter-currents usually present to contradict too-easy generalizations.''
Lofty though her views might be, Mrs. Tuchman was down to earth in her research. Before she wrote ''The Guns of August,'' she rented a Renault sedan and toured the appropriate battlefields. When she took notes, it was always on index cards measuring 4 by 6 inches - a convenient size, she said, for storing in shoeboxes and carrying in her purse.
That sort of prosaic concern was far from her exalted birthright. Barbara Wertheim was born on Jan. 30, 1912, in New York, the daughter of Maurice Wertheim, an investment banker, art collector and philanthropist, and Alma Morgenthau Wertheim, a sister of Henry Morgenthau Jr., who was Secretary of the Treasury under President Franklin D. Roosevelt.
Miss Wertheim attended the Walden School before entering Radcliffe College, where she concentrated on history and literature and received her bachelor's degree in 1933. Worked in Japan
Since, as she put it, ''paying jobs did not hang from the trees'' in that Depression year, she took an unpaid position with the American Council of the Institute of Pacific Relations.
The following year, she went to Tokyo to help work up an economic handbook of the Pacific area. While there, she wrote for two journals, Far Eastern Survey and Pacific Affairs.
An early contribution was a review of a French historian's book about Japan. Not long after it was printed, she later recalled: ''I was thrilled to receive from the author a letter addressed 'Chere consoeur' (the feminine of confrere, or as we would say, 'colleague'). I felt admitted into an international circle of professionals.''
In 1936, Miss Wertheim went to work for The Nation, which her father had bought to keep it from going bankrupt. Her first job was clipping newspaper articles, but soon she was writing herself, and in 1937, during the Spanish Civil War, she went to Valencia and Madrid as The Nation's correspondent. 'Heroes, Hopes, and Illusions'
From Spain she traveled elsewhere in Europe, savoring what she later called ''a somber, exciting, believing, betraying time, with heroes, hopes, and illusions.''
In London, she put together a short book, ''The Lost British Policy,'' about British policy toward Spain and the Western Mediterranean. Her later appraisal of the work, which came out in 1938, was that it was only ''a respectable piece of research,'' and she sometimes omitted it in listing her books.
By 1939, she was back in New York, writing largely on Spain, and the next year she married Dr. Lester Reginald Tuchman, a New York internist.
Mrs. Tuchman was soon showing her strength of will. With Nazi Germany looming, she later wrote, her husband ''not unreasonably felt at that time that the world was too unpromising to bring children into.
''Sensible for once, I argued that if we waited for the outlook to improve, we might wait forever, and that if we wanted a child at all we should have it now, regardless of Hitler.''
''The tyranny of men not being quite as total as today's feminists would have us believe,'' she added, writing in 1981, ''our first daughter was born nine months later.'' Separated by Wartime
After Pearl Harbor, Dr. Tuchman went overseas to a United States military hospital, and Mrs. Tuchman got a job in New York with the Office of War Information, preparing material on the Far East for use in broadcasts to Europe.
''After the war, when my husband came home, we had two more children, and domesticity for a while prevailed,'' she wrote later, ''combined with beginning the work I had always wanted to do, which was writing a book.''
''When the children were very small,'' she once recalled in an interview, ''I worked in the morning only and then gradually, as they spent full days at school, I could spend full days at work. I could never have done any of this work if I hadn't been able to afford domestic help.''
The fruit of those labors, ''Bible and Sword,'' about relations between Britain and Palestine, came out in 1956. It attracted relatively little notice, though what there was of it was favorable.
Two years later ''The Zimmermann Telegram'' appeared, about a message sent from Berlin to a German diplomat in Mexico in January 1917, raising the possibility of ''an understanding on our part that Mexico is to reconquer territory in Texas, New Mexico and Arizona,'' and about the message's repercussions after it was intercepted and made public by the British.
Writing in The New York Times, Samuel Flagg Bemis, the Yale diplomatic historian, said the value and importance of the book lay in Mrs. Tuchman's ''brilliant use of well known materials, her sureness of insight and her competent grasp of a complicated chapter of diplomatic history.'''The Guns of August'
Attempting something that might have seemed a bit beyond her reach, Mrs. Tuchman took up a far broader and more important topic in her next book, which was ''The Guns of August.'' World War I, as she saw it, was no less than ''the chasm between our world and a world that died forever.''
Though the book was largely about arms and men, it was also about aspirations and ideals. ''Men,'' she concluded, in one widely quoted passage, ''could not sustain a war of such magnitude and pain without hope - the hope that its very enormity would insure that it could never happen again.''
Clifton Fadiman, writing in the Book-of-the-Month-Club News, said: ''Its virtues are almost Thucydidean: intelligence, concision, weight, detachment.''
Writing in The New York Times, Cyril Falls, a British officer turned military historian, said Mrs. Tuchman ''writes so brilliantly and inspiringly.'' The book, he said, was ''lucid, fair, critical and witty.''
But he contended that her performance was uneven, and ''the errors and omissions amount to a formidable total.'' For his part, Bruce Bliven, writing in The New Yorker, complained that ''Mrs. Tuchman leans toward seeing issues as black and white.'' Emphasized Human Qualities
The book's emphasis on the human qualities of the leaders of the time helped make it popular with the public, and it served as the basis for a 1964 documentary film, produced by Nathan Kroll, with the same title.
The quarter-century preceding World War I was the subject of Mrs. Tuchman's next book, ''The Proud Tower,'' which came out in 1966. In a review in The New York Times, Martin Duberman, a Princeton history professor, praised her skill at narrating events, making historical personages come alive, and writing clearly and powerfully about complex matters.
But he said the book did ''not come up to the high level of 'The Guns of August.''' It was not a portrait of the period, he contended, but merely ''random brush strokes, leaving a canvas unoccupied by any ruling vision.''
When ''Stilwell and the American Experience in China, 1911-45,'' came out, it was hailed as ''brilliant'' in a review in The New Republic by the dean of American China scholars, John K. Fairbank, the director of Harvard University's East Asian Research Center. 'A Distant Mirror'
Another book about Asia, ''Notes From China,'' a slim volume about a six-week trip Mrs. Tuchman had taken, appeared in 1972. But six years went by before the appearance of her next work, ''A Distant Mirror,'' a study of the 14th century, an era that was racked by plague and war.
Reviewing the book in The New York Times, Eric Cochrane, a professor of history at the University of Chicago, said, ''This book abounds in the same elements that have made her previous books masterpieces of popular scholarship: vivid battle scenes, scenes from daily life, brilliant portraits.'' But he also argued that she was guilty of grave omissions and misinterpretations.
In ''The March of Folly: From Troy to Vietnam,'' a 1984 book, Mrs. Tuchman scrutinized the Trojans' decision to admit the Greek horse into their city, the refusal of six Renaissance Popes to arrest church corruption in advance of the Protestant Reformation, British misrule under King George III and America's mishandling of the Vietnam conflict.
Mrs. Tuchman had an occasional fondness for twitting figures of authority. She once began a speech to the Army War College by noting that her subject, generalship, had been suggested by the college's commandant.
''No doubt,'' she observed, ''he could safely assume that the subject in itself would automatically interest this audience in the same way that motherhood would interest an audience of pregnant ladies.''
Mrs. Tuchman is survived by her husband, who is an emeritus professor of clinical medicine at the Mount Sinai School of Medicine; a sister, Anne W. Werner of Manhattan; three daughters, Lucy T. Eisenberg of Los Angeles, Jessica Tuchman Mathews of Washington, and Alma Tuchman of Cos Cob and Manhattan, and four grandchildren.
The funeral will be private. A memorial service is be held at 2 P.M. Sunday in the Celeste Bartos Forum at the main branch of the New York Public Library. Her Books And the Subjects ''The Lost British Policy'' (1938): British policy toward Spain and the Western Mediterranean.
''Bible and Sword'' (Alfred A. Knopf, 1956): Relations between Britain and Palestine.
''The Zimmermann Telegram'' (Alfred A. Knopf, 1958): A 1917 diplomatic message and its international repercussions.
''The Guns of August'' (Macmillan, 1962): The background and beginning of World War I. ''The Proud Tower'' (Alfred A. Knopf, 1966): The quarter-century preceding World War I. ''Stillwell and the American Experience in China, 1911-45'' (Macmillan, 1971): A biography of Gen. Joseph W. Stillwell. ''Notes From China (Macmillan, 1972): A trip to China.
''A Distant Mirror'' (Alfred A. Knopf, 1978): The 14th century.
''Practising History'' (Alfred A. Knopf, 1981): A collection of her shorter writings.
''The March of Folly: From Troy to Vietnam'' (Alfred A. Knopf, 1984): Some historical mistakes.
''The First Salute'' (Alfred A. Knopf, 1988): The American Revolution placed in an international perspective.
photos of Barbara Tuchman (NYT) (pgs. A1 & B7)