ONE DAY IN EARLY JANUARY 1963, David Halberstam, portable typewriter in hand, appeared at the ground-floor apartment I was renting on a side street in Saigon. The front room served as an office. I slept in the second room at the back. I was the correspondent for United Press International, and David was in Vietnam for The New York Times. It was typical of the man that he did not ask, “May I join you?” Although wire-service reporters and daily-newspaper journalists often teamed up overseas, he simply assumed he would be welcome and set his typewriter down on the other side of the table I used as a desk. That day was the beginning of a partnership and, in later years after our assignments in Vietnam were over, a friendship that was to endure until he was killed in a car crash in California last April.

There were no secrets between us. On days when we were both in Saigon, rather than out in the countryside reporting on the fighting, we would fix on a story we sensed was ready to be told, set off separately to see our sources in order to limit their exposure and then share everything we gleaned.

Vietnam in 1963 was something unimaginable to most Americans, still basking in the triumphant glow of the Second World War. The conflict was being lost, but the commanding general, Paul Harkins, and the ambassador in Saigon, Frederick Nolting, insisted that victory was around the corner. Harkins and Nolting accused us and the other American reporters of spreading falsehoods. We were politically suspect. We ought to be fired. Many of our editors doubted us. David was just 28 when we teamed up, and I was 26. How could these kids be right when a four-star general and a senior diplomat said they were absolutely wrong?...