The little observation plane was flying low over the jungle, towards a grid reference where a team of US marines had radioed for help. Seated behind the pilot, a 23-year- old lieutenant named Karl Marlantes was watching the ground and wishing the weather would clear. In this uneven war in Vietnam, clear skies gave the Americans the advantage. Fog favoured the indigenous troops.
Recalling the incident from the comfort of a Bloomsbury hotel 40 years later, Marlantes hesitates, unsure whether it is wise to go on with the story. "Do we want to go into this?" he asks.
Yes, I want to go into it, because the ex-lieutenant has recently achieved sudden fame as an articulate witness to a war that holds a unique place in Western culture. I am curious to know what the witness saw.
He continues in a detached tone, neither boastful nor self-justifying: "A reconnaissance team had got into trouble. A fairly good-sized unit were chasing them through the jungle, and they couldn't find a place to extract from.
"There were horrible clouds so we couldn't get any jet aircraft in. I had an M16 [automatic rifle] with me. The windows had been shot out from the aircraft long ago. The pilot put it into a sideways slip between the recon team, and I fired at them from out of the window. I remember hitting a couple of them."
In other words, with his rifle he killed a couple of teenage boys in Vietnamese uniforms doing what they had been told to do. From here, the story gets worse: "The marines got up on a hill, and the North Vietnamese were coming up the hill after them, when the weather cleared – just enough. I directed in a couple of jets who hit them with 500lb bombs, and napalm.
"It was unbelievable after that, to see those bodies charred, some of them still crawling around, and I knew it was just directly me. I was exultant because I had saved the recon team. I said to the pilot: 'We've got crispy critters all over this hill!'"
This same man who once derived such a high from bringing agonising death to teenage conscripts is now a thoughtful 65-year-old, who has written a sensationally successful novel. Matterhorn, a 600-page epic, is shaped like an adventure story except that it is an adventure without meaning. Every feat of physical endurance, every act of bravery, the comradeship, the horrible injuries and the violent deaths – they all have no point.
The general futility is shown up in the circular journey taken by Bravo Company, the central characters of the story. They begin on a hill near the North Vietnamese and Laos borders which the Americans have nicknamed "Matterhorn".
Although they are exhausted by their constant patrolling of the surrounding jungle, they are ordered to construct bunkers to defend the hill. On the day that task is done, orders change. They have to leave the hill, for the jungle. In their absence, the North Vietnamese move in, and Bravo Company ends up being slaughtered in an uphill assault against their own defence works.
For most of the narrative, however, they are in more danger from the climate, the leeches, mosquitoes and tigers, the stupidity of officers and their own murderous quarrels than from the Vietnamese. The adrenaline rush they experience from killing their teenage enemies is like a perk that makes soldiering worthwhile.
What makes this grim narrative so compelling is the wealth of meticulous detail, the sharply drawn characters, and the author's insight into how large organisations function. If the circumstances were not so extreme the relations between frontline troops, their officers, and the senior brass back at headquarters could be the story of management and employees anywhere. I was told that each time Marlantes steps into a television studio to publicise the book someone tells him: "It's exactly the same here!"
That he is able to move so confidently between generals and enlisted men is a by-product of the epic struggle he had finding a publisher.
He started writing what he hoped would be the definitive Vietnam novel round about the time that North Vietnamese tanks were finally rolling into Saigon, in 1975. When he started looking for a publisher two years later he found that "they didn't even read it, because there was no market for Vietnam. I would get comments like, 'It sounds pretty long. We don't do big books.'"
When it eventually reached a publisher many years later, it was – oddly – through a chain of women. This is odd because the book has no female characters, except in one brief scene in a military hospital. Yet the first professionals to recognise its merit were all women. The first person to read it professionally was a senior editor in a tiny, not-for-profit publishing firm called El Leon, in Berkeley, California. She persuaded her boss to produce a print run of 2,000 copies. The book was submitted for a prize sponsored by the Barnes & Noble book chain, where it was read by a woman volunteer, who enthused about it to the woman who ran the programme, who passed the recommendation on to her boss – Barnes & Noble's senior buyer of fiction. It was she who persuaded a mainstream New York publisher to take it up.
Meanwhile, frustrated in his ambition to be a published novelist, Marlantes had spent the intervening decades working as an energy sector consultant, and for a time as managing director of a Singapore-based firm producing batteries, periodically disappearing into the basement at home to continue work on the book.
Writing it was a kind of therapy, as he had left Vietnam suffering from what we now know as Post-Traumatic Stress Disorder. As well as visiting death upon others, he had come close to it himself several times. The first time was on about his third day in Vietnam, when he was one of a company of soldiers taken by helicopter to do patrol duty in the jungle.
"I didn't even have to hit the ground before I got shot at," he said. "The first thing I remember was sitting with my back against the bulk-head, and pht-pht-pht-pht-pht – holes started appearing in the skin of the chopper, and I went, 'Oh my God, they're shooting at me!' Of course, I didn't think 'us'. I took it personal."
About a week later, his company came upon a Vietnamese patrol guarding a jungle hospital. One of the young marines took a bullet that went through his breast pocket into his heart. It was the first time that Lt Marlantes had seen someone being killed.
In the dead youth's pocket he found a photograph of his girlfriend, her face obliterated by the bullet. "It just was stunning. If you wrote it in a novel you would say that's hokey to have the bullet go right through the girlfriend's face. It was so poignant to me, because it was a high-school photograph."
At this point in our conversation, the normally articulate writer stumbled over his sentences: "I can get into tears just thinking about...His name was..." He gave the dead teenager's name, but immediately pleaded, "Don't put that in, please. I remember him so well."
Another killing he was involved in made it into the novel almost as it happened. Several months into his time at war, he came face-to-face with a young Vietnamese soldier wielding a grenade. Marlantes had his rifle trained on the soldier, but instead of experiencing the kick he sometimes got from killing, he found himself wanting to spare the teenager's life. "I don't know what it was. I think it was because our eyes had contact. We called them 'gooks'; we didn't think of them as kids. But here was a kid looking me right in the eye and I didn't want to kill him, but he threw the grenade at me and I did."
Marlantes had joined the Marines reserve after leaving high school, but had not immediately been sent to Vietnam. As a reserve officer, he started at University College, Oxford in 1967, holding a Rhodes Scholarship a year ahead of Bill Clinton. But he was overcome by guilt that he was "hiding behind privilege" instead of fighting in the war in which five boys from his old high school, in a small town in Oregon, had already died.
He took out all his scholarship money and absconded to Morocco, before reporting early for active duty dressed in "a djellaba and yellow slipper shoes, smelling like a camel, and with hair down to my shoulders". He was sent to Vietnam, where he served for just over a year, assuming he would never see Oxford again.
On leave in the US he developed symptoms of a mental breakdown, including heavy reliance on alcohol and drugs. He was also badly affected by the reactions of contemporaries who had turned against the war, and who now saw the marines as killers of innocent Vietnamese.
On one occasion, he was trying to make an impression on a woman he fancied. Sitting on the steps of her apartment block, he confessed that he had been in Vietnam as a marine. "They were the worst!" she exclaimed, and turned to walk back into the building and out of his life.
It was during this personal crisis that deliverance came in the form of a letter from Sir Edgar Williams, the former British army officer who ran the Rhodes Scholarship scheme, telling him that a sum exactly the matching the amount that he had blown in Morocco awaited him in a branch of Barclay's Bank in Oxford High Street. "That's all he said. I just started crying. I knew it meant that I could come back to Oxford," he said.
But his symptoms would return with a vengeance some years later. Walking into a board meeting in Singapore, he saw corpses piled on the table, and realised he would have to quit his job and seek therapy.
Despite what he has been through, Marlantes has been accused of glossing over the worst of what we know about the Vietnam War to tell a story that vindicates the young men sent out to fight. He omitted some of what he himself saw, including the dreadful effects of napalm. Edward Wilson, another Vietnam veteran who has written a less acclaimed novel, has furiously denounced Marlantes's work as "cartoon war porn of the lowest sort". Marlantes's answer is that he has written a novel, not a political tract.
"Does [Wilson] call Wilfred Owen and Tolstoy pornographers because they reveal an actual reality that humans go through?" he demanded. "This is fiction. My characters are 19-year-olds and are not highly educated. They do not think about the politics, and this book is not about politics. My own view about the war is that we killed hundreds of thousands of Vietnamese and dropped Agent Orange all over the country, not to mention killing 60,000 of our side. Those are my politics. If that's what you set out to do, to write a political book, maybe you should stick to history.
"My characters would not think of that and, let's face it, most of the people who were doing the fighting in the war were like my characters. The ones who thought otherwise stayed home."
Another factor is that he spent his months in the jungle near the border, where there were no villages and no guerrillas. Atrocities like the massacre of villagers in My Lai took place many miles further south. Yet even in this novel, the fighting men with whom he identifies so strongly are depicted cutting off the ears of dead Vietnamese for souvenirs.
And there is an almost throwaway sentence in which the reader is told that the US soldiers are casually killing enemy soldiers who have their hands up. In battle, they are overcome by blood lust which makes them exult in death.
One of Marlantes's disturbing claims is that almost any teenager who is given a weapon and thrown into a situation such as this will get a high out of inflicting violence on his opponents.
"I call it the Mad Monkey. My guess is that anybody put into that situation, when it's a matter of saving their side, would exalt when it happens. Some people would claim that they'd say 'no'. They're just kidding themselves. Or maybe there are some people who are probably much more peaceful than I am. I did join the marines." If he is right, we can expect worse stories than his to come out when veterans start writing dispassionately truthful accounts from Iraq or Afghanistan – where the killing may be more impersonal if the killer is rarely close enough to make eye contact with his victim.
"I have always been happy that we didn't have the moral dilemmas that they're facing in Afghanistan or that the [US] army faced [in Vietnam] with villagers and Vietcong. With us, anything that moved was a North Vietnamese soldier in uniform, so there was none of this horrible moral dilemma which our kids are facing now. We call them soldiers or marines, when actually they're just kids. It is a shame to put 19-year-olds into that position," he said.
'Matterhorn' by Karl Marlantes (Corvus, £16.99). To order a copy for the special price of £15.29 (free P&P) call Independent Books Direct on 08430 600 030, or visit www.independentbooksdirect.co.uk