David Halberstam, who has died aged 73 in a car crash in California, was one of the most talented, influential and prolific of the American journalists who came of age professionally in the 1960s. He was one of the small group of young reporters - with his New York Times colleague Neil Sheehan, Stanley Karnow of Time magazine and Malcolm Browne and Peter Arnett of the Associated Press - who, having initially accepted the reasons for the Vietnam war, came to believe, first, that it was not going as well as Washington maintained, and later that it was ill-conceived and unjustified.
Halberstam and his colleagues eventually persuaded a decisive slice of American public opinion to question the war's rightness. He first described how things had gone wrong in his 1965 book The Making of a Quagmire, and in 1972 drew on his years of experience of the war, reinforced by a heroic schedule of interviews, to write The Best and the Brightest, an unsparing critique of the gifted men in the Kennedy and Johnson administrations who blundered into humiliating defeat.
A fairly tall, good-looking man who had been a good athlete in high school, Halberstam had a quiet, thoughtful manner that helped him to persuade people to open up to him in interviews. In the middle of his career, he established himself as a gifted and perceptive popular historian and wrote an enjoyable and influential history of the 1950s. In recent years he turned himself into an enthusiastic, if at times romantic, chronicler of baseball and other American sports.
When he was killed he had just been talking about The Coldest Winter, his forthcoming book about a battle in the Korean war, and was on his way to interview Y.A. Tittle, a legendary American football quarterback of the 1950s and 1960s.
After the World Trade Centre atrocities of September 11 2001, Halberstam wrote an account of the team from his own local fire station in New York, Engine 40, Ladder 35, which lost 12 men in the catastrophe. Like many of his books, it dealt sensitively with the motivations for courage, with male friendship and the sense of honour that impels men to face fearfully dangerous duty.
Halberstam researched meticulously, transcribing dozens and, for some books, hundreds of interviews in longhand. He wrote rapidly, and learned to shut himself away either in New York or in a holiday home at Nantucket, an "iron-clad discipline" that enabled him to write two books in the 1960s, three in the 1970s, four in the 1980s, and six in the 1990s. He was scrupulously fair and had an instinctive grasp of the context and import of the story he was telling. If he had a fault, it was a taste for emotion, sometimes brushing sentimentality.
David Halberstam was the son of a surgeon and a teacher. He was born in New York City, but after moving all over the U.S. when his father was in the army during the second world war, the family settled in Yonkers, half an hour north of where he was born. He went to high school there and then studied journalism at Harvard. After graduating in 1955, instead of going to work for one of the big media companies in New York, he headed for West Point, a small town in Mississippi.
It was the year after the supreme court's momentous decision banning school segregation, and Halberstam soon became fascinated by the human tensions of the racial crisis. He went to work for the Nashville paper, the Tennessean, and there got to know the group of young activists, led by the Rev James Lawson, whom he celebrated in a 1999 book about the civil rights movement, The Children.
It was not long before he was picked up by the New York Times, who packed him off to the Congo to cover the upheavals consequent on the abrupt collapse of Belgian colonial power there and on the Kennedy administration's fear that the Soviet Union would take advantage of that situation. Before long he was sent to Saigon, where he stayed from 1961 to 1964.
He and his friends and colleagues took advantage of the American military's willingness to helicopter them into combat situations. It was not long before they, with Halberstam always a leader among them, began to question the bland confidence of the official line as peddled at the so-called "five o'clock follies", the daily press conference at the American headquarters in Saigon. In 1964 his work received the ultimate accolade for an American reporter, the Pulitzer prize.
Later politicians, Lyndon Johnson and Richard Nixon among them, questioned Halberstam's honesty and even his patriotism. They misunderstood a passionate, if generally soft-spoken, belief in the goodness of the American system. Halberstam and his friends questioned and criticised American policy and military conduct in Vietnam, not out of a lack of patriotism, but out of their conviction that the U.S. must conduct itself according to the highest possible standards.
Late in his life, he became gently critical of the style and conduct of the Bush administration.
Halberstam was married twice. In 1966, while working in Poland, he wed the actor Elzbieta Czyzewska. The next year they were both expelled because of his critical reporting on the communist regime. In 1977 the couple divorced and he married Jean Sandness Butler in 1979. She survives him with a daughter Julia.
David Halberstam, journalist and writer, born April 10 1934; died April 23 2007.