The influence of the journalism of the Vietnam war on correspondents abroad - whether it's been read and remembered or merely imbibed as lore - has been incalculable. In Central America during the 1980s, where the presence of American advisers in El Salvador and the possibility that Ronald Reagan might order an invasion of Nicaragua gave the whole story a tantalising whiff of history about to repeat itself, there was always a special frisson if a Vietnam veteran correspondent turned up. Saigon was a synonym for a kind of styled wisdom. It rarely mattered how much time someone had spent there, what they had written or how much they had seen beyond the terrace of the Continental Hotel. There would be some other hotel to return to after a day in the violent countryside where a cheery barman, cold beers and a fan spinning through the moist, tropical air would supply the imaginative dimensions of the Continental.

The lasting motif of the Saigon style, even among those who never practised it to the full, was a kind of rock'n'roll bravado. This quality was the key to the success of Michael Herr's book Dispatches, included in its entirety in Volume II of these beautiful, missal-like editions with their flimsy, fine paper and tassel bookmarks. Readers of Dispatches often remember Herr's portrayal of dissolution: the corruption of Saigon and the drug-taking and rebellious indiscipline of the GIs as the American war effort collapsed on itself. But that was only the half of it. The most powerful theme of Herr's book and of many of the pieces by American correspondents collected here is the fear and terror of the war.

These correspondents were able to experience this because they were free to travel wherever they wanted and take such risks as they dared. Their relationships with the soldiers fighting the war and their contempt for the daily official briefings were forged by exposure to combat in the most appalling conditions.

If you want some idea of what it may have been like to have been under one of Nato's bombing mistakes in Yugoslavia, you would do well to read John Saar. He describes being in the centre of a cluster-bomb attack by an American plane on a North Vietnamese unit - friendly fire as "a blizzard of steel". In piece after piece there is a minute accounting of violent death and injury. Jack P Smith - then a serving officer, later a correspondent - writes of the massacre of half a company at the battle of Ia Drang valley in November 1965. In Cambodia eight years later, Sydney Schanberg (whose articles were the inspiration for the film The Killing Fields) describes the destruction of an entire town in an accidental bombing by a B-52.

Reading these reports and vignettes one after another induces a sensation of entrapment and breathlessness, a feeling of how, under prolonged mortal threat, there is no future, only an inescapable present. Herr conveys this very well in his account of the American base at Khe Sanh, besieged for months in 1968 by incessant artillery bombardment. So do others such as Ward Just, describing how it felt to be caught up in a lengthy ambush: "Your movements become slow and deliberate and your consciousness seems to move back in time."

The remarkable thing about most of the reportage in the book is the diligence it took - the precision and accuracy of names, dates, sequences of events in battle - and its honesty. Most of these writers are self-aware but rarely self-regarding, particularly in their own humanitarian capacities. When they describe their own feelings there is disgust, fear, voyeurism and humour, but no postures of high-minded compassion, sanctimony (save a congenital reverence for American motives) or crowd-pleasing sentimentality.

In the early days the American correspondents saw the war as a legitimate consequence of America's global involvement and could not see how the American republic had come to resemble the French empire before it in Indochina. The correspondents' early clash with the Kennedy administration was not about the purpose of the war but the methods used to pursue it. They wrote about how the North Vietnamese army was running scared and not up to the job. When Lyndon Johnson, terrified of being called a coward, pressed on with the war, the American correspondents slowly lost faith. But their notions of American innocence and benevolence never really melted, which is why they missed atrocities such as the My Lai massacre.

In the end this collection is about Americans and rarely about the Vietnamese or even about the communism that was the target of the American mission. These writers are much better on how Americans endured despair than on how the Vietnamese inflicted it. There are rare glimpses of another mentality, such as a long piece based on extracts from the diary of a dead North Vietnamese soldier, Mary McCarthy's account of the bombing raids on Hanoi and Frances FitzGerald on the Mekong Delta. But mostly the work here induces a sense that Vietnam was not a place but an evil state of mind in which all those names of real locations - Hue, Highway 1, Con Thien - were merely poisonous disorders of the American psyche, to be examined with horrid satisfaction.

Some of this is still very powerful. One of the best pieces in the collection is by Gloria Emerson, about her room at the Continental Hotel: "In the last month of that endless year nothing in the room spoke of any season at all, or of how many had died or of anything I had seen." She leaves Saigon with a deadened sense of purpose: "There are other stories I could tell, about the living and the dead . . . but so very much has already been written and none of it ever made any difference at all."