Associated Press journalist Peter Arnett poses next to the wreckage of an American warplane near Saigon in October 1965.

In the early years of the war, American correspondents went to Vietnam with faith in the "domino theory," which held that it was necessary to contain communism before it spread across the globe to threaten the United States. But the confusingly complex reality of the conflict inevitably hit them as hard as the sight of the withered hand tacked to the wall of the Associated Press bureau in Saigon. As Pulitzer-winning correspondent Peter Arnett once recounted, the grisly souvenir — brought back from an ambush scene by a photographer — was a reminder to neophytes and journalistic veterans alike that beyond the luxurious confines of Saigon's hotels and cafes, a brutal war was going on.

Though U.S. official briefings — which came to be derided as "the Five O'Clock Follies" — painted a sanitized, fantastically optimistic picture of the war's progress, correspondents were also allowed a surprisingly free rein to go wherever they wished in pursuit of the actual story. As a result, many of them came to question not just U.S. tactics and strategy in Vietnam, but the very justification for the war itself.

The influence of those disillusioned journalists had a profound effect on American public opinion. By the mid-1960s, more than nine out of 10 American households had television sets, and nightly reports filled with combat footage — flown to Tokyo and beamed by satellite to the United States — drove home a powerfully disturbing message.

The climax, perhaps, was when Walter Cronkite, the veteran war correspondent turned evening news anchor, returned from a trip to Vietnam in 1968. Jettisoning any pretense of journalistic detachment, Cronkite argued that it was time to end the war: "It is increasingly clear to this reporter that the only rational way out ... will be to negotiate, not as victors, but as an honorable people who lived up to their pledge to defend democracy, and did the best they could." He would get his wish — but not for another five years, at which point many more American and Vietnamese lives had been lost.