In the humid hell of the Vietnamese jungle, during one of the more stupid and dismal wars of the 20th century, Lieutenant Mellas, the recently arrived rookie marine officer, worries. By nature he is more of a politician than a soldier. And, at the start of Karl Marlantes's first novel, Mellas is more concerned with his ambition than with anything else. Will he get advancement? Has he said the right thing? Will he be discovered to be a coward?

The publishers of Matterhorn are making much play of the authenticity of the book: it has been 30 years in the writing, and the author was a young marine officer who saw action in the Vietnam war; indeed, my review copy came accompanied by a copy of his award of the Navy Cross, which cites his "extraordinary heroism" in a combat operation that sounds very much like the action in his novel. Except, none of that matters to us. Probably the best war novel in the English language is The Red Badge of Courage. It was written by Stephen Crane, who received grateful fan letters from American civil war veterans who assumed he was an ex-colleague, so vivid and true was Crane's novel about a conflict that in fact had ended six years before his birth. Matterhorn, the tale of a campaign to take a hill, quaintly code-named for an Alpine mountain, with all its ugliness and blood and fear, presents itself as fiction, not memoir, and therefore has to be read, and judged, as such.

Marlantes, maybe because or possibly despite his own experience, is entirely convincing on the mess of war, tropically damp, teeming with disease, in a world criss-crossed by dividing lines that have little to do with the notional enemy. Senior officers are in conflict with junior officers; all the officers are in conflict with the enlisted men; there's white against black; short-term marines against those who are in the Corps for life. "He ran as he'd never run before, with neither hope nor despair. He ran because the world was divided into opposites and his side had been chosen for him, his only choice being whether or not to play his part with heart and courage." And despite the barrack-room vocabulary of its protagonists, this is a very chaste book: women are hardly here at all, except as faraway romantic images to yearn for vaguely.

A map of the theatre of combat is helpfully placed at the beginning of the book and a glossary, even more helpful, at the end. The reader can sometimes struggle to make sense of all the acronyms and armaments and slang, M-60s and M-79s, the grimly sarcastic RHIP ("Rank Has Its Privileges") and the difference, for example, between "fragging" and a "frag order". (A frag order is merely an additional, precise instruction added, for security's sake, to a more general order. Fragging is the marine term for murdering a superior by throwing a grenade into his living quarters or foxhole.)

But even with this confusion of names and numbers, Matterhorn is tremendously compelling to read. It begins with dangerous moments that presage the worse that is to come. A leech gets stuck inside a sergeant's penis, a black marine fights to keep his afro; these are among the daily battles fought in discomfort and misery as they wait for war to find them. And as the war does find them, Matterhorn bustles the reader along with the urgency of its own telling, the aghast descriptions of lives of perpetual degradation, marching and hand-to-hand combat, endured by men who have already been driven beyond their own limits, partly by the exigencies of war and partly by the whims and vanities of commanding officers: "Fitch pulled the company into the smaller circle of holes. There were no longer enough marines to defend the outer perimeter. Mellas tried to ease the pain in his throat and tongue by licking the dew on his rifle barrel."

These are heartbreakingly young men. The lieutenants and captains are in their early twenties. Most of the men they command are still teenagers: "Mellas nodded back, watching Hippy's face. It was just the face of an 18-year-old kid with a peace medallion around his neck. Hippy wore a pair of wire-rimmed glasses, had straggly hair, and had the beginnings of a beard. An ordinary human face. Mellas had never really looked at one before."

By the end of the book, Mellas has changed utterly. The rookie has become a veteran. He is no longer bound up in his own ambition. He has been tested and, by battle logic, has proved himself. But he has lost a lot; he is damaged physically, maybe morally. Wounded in war, patched up, promoted, he returns to the jungle and sees the new intake of troops. "There were some things he couldn't tell the uninitiated. For them, the bush should, and would, remain a mystery." Marlantes's achievement is that he has made it less mysterious.

Karl Marlantes
Corvus, 608pp, £16.99

David Flusfeder's latest novel is "A Film by Spencer Ludwig" (Fourth Estate, £11.99)

This article first appeared in the 16 August 2010 issue of the New Statesman, The war against science