When we met in Saigon in May 1963, David Halberstam was only 29, but he was already the dominant figure among an influential group of journalists who reported what they observed even when it contradicted the version of the war put out by the military. This was daring stuff; only 18 years after World War II, reporters were not supposed to question senior American military commanders. It was such a serious matter that President Kennedy asked New York Times Publisher Arthur Sulzberger to reassign Halberstam, a request Sulzberger rejected.

In the decades since, Halberstam and his colleagues often have been blamed by right-wing commentators and some military officers for the loss in Vietnam, on the grounds that their reporting undermined domestic support for the war. This is, of course, nonsense; in war, success speaks for itself. Spin may delude the public for a while, but not indefinitely — and meanwhile people die. The basic truth is simple: Halberstam’s reporting was right, and the official version was not.

I can still see David the first time we met: Everything that evening seems now to have foreshadowed his future and our complicated but lasting friendship. A week after I arrived in Saigon, as a young Foreign Service officer on his first overseas assignment, I presented David with a letter of introduction from a mutual friend. With his characteristic generosity, he invited me to dinner at one of Saigon’s best French restaurants, bringing along his closest friend, United Press International bureau chief Neil Sheehan, who later described the evening in his book “A Bright Shining Lie.” They seemed a generation older and wiser than I, but — and I realize this now with astonishment — all of us were in our 20s.

They were tall and intense and noisily exuberant. They knew they were covering the biggest story in the world, with very few competitors. They knew the official version was wrong, and they were going to get the truth out — not to bring down the American mission but to help it find its way.

At that time they still supported the war. They wanted those who were lying to the public, both the corrupt South Vietnamese government and American military commanders, to be held accountable.

They especially despised the senior commander, World War II veteran, Paul Harkins, and after giving me some advice — “Don’t trust anything those bastards tell you” — David and Neil spent most of the evening denouncing Harkins.

After some wine, they conducted a mock trial of the four-star general for incompetence and dereliction of duty. In his rumbling, powerful voice, David pronounced Harkins “guilty ” of each charge, after which Neil loudly carried out the “sentence”: execution by imaginary firing squad against the back wall of the restaurant. As others listened with astonishment, I looked around in alarm, certain that if I was recognized, my career would be over before it had begun.

In late October 1963, in a fever pitch of excitement, David and Neil took me to lunch and, whispering conspiratorially, told me that a coup against the Saigon government would begin right there and then. Every few minutes one of them would run outside to look for troops marching on the presidential palace. When lunch ended without a coup, Neil left for a brief vacation in Tokyo and David stayed on. The coup happened a week later, exactly the way they had predicted, and David won a Pulitzer for his work that year.

He moved on, leaving the Times to write a book that would change forever perceptions of the American elite. No book of its sort has had a greater impact since. He called it “The Best and the Brightest,” and it is still a revelation, and, in the age of Iraq, unexpectedly relevant.

Studying the background and values of the men around Kennedy and Lyndon Johnson, Halberstam created a brutal portrait of people far too sure of themselves, certain that they knew what was best for the nation and the world — but woefully ignorant of the distant land to which they were sending young American soldiers.

In long, overpowering sentences, he conveyed deep anger and a sense of betrayal. As with Harkins, he wanted to hold high officials accountable. His primary targets were the defense secretary, Robert McNamara, and the national security adviser, McGeorge Bundy, two of the smartest men ever to serve in government. By the time Halberstam finished exposing their arrogance and ignorance, they were never perceived the same way again.

He wrote a second book in what amounted to a continuing study of America and war, “War in a Time of Peace,” on Clinton and the Balkans, and before his death last week had just completed a third, on the Korean War, that will come out this fall.

One can only imagine what he might have written about Iraq.

Mr. Holbrooke is a former U.S. ambassador to the United Nations.