Soldiers of Salamis, Javier Cercas, trans. Anne McLean

Boyd Tonkin salutes a commanding novel of war's myths and memories

How long does it take for the miseries of modern war to breed classic works of literature? If that war started in another country, posed stark moral questions for the whole world, and offered foreign authors a brief, life-changing exposure to its comradeship, perils and betrayals - then not very long at all. George Orwell published Homage to Catalonia even before Franco's forces had taken Madrid and Barcelona.

But what if the aftermath of war - Spain's civil war - also left a nation littered with bereaved families, broken friendships and shattered hopes, all framed by 35 years of dictatorship and denial, followed by 25 years of democracy and denial? Then a sensitive writer might, like the narrator of Soldiers of Salamis, look back after six decades and still feel at first that the conflict promised only "excuses for old men's nostalgia and fuel for the imagination of unimaginative novelists".

Soldiers of Salamis - which has deservedly won half a dozen prizes in Spain - shows how, and why, one 40-year-old author found that the half-buried trauma of civil war could yield more than elderly comrades' yarns or stale propaganda. The heart of this novel, Javier Cercas's third, re-tells an extraordinary "true tale", "cut from the cloth of reality" and dating from the final days of war in January 1939. Just as importantly, it takes us down the road that leads a Spanish writer from cynical indifference through antiquarian fascination to wholehearted empathy - a progress that gives this book its singular, and satisfying shape. More than 60 years on, Cercas has written a classic novel - though a consistently droll and high-spirited one - about the filtration of war's tragedies through memory and myth.

Our narrator shares the name "Javier Cercas", and some of the actual author's biography. A jobbing journalist and minor novelist living in the Catalan city of Gerona, he comes across as a bumbling, self-effacing dilettante. A running joke has Javier meet someone who claims to have read his books and quip: "So you were the one, were you?".

In search of an original theme, Javier ferrets out the true story of Rafael Sánchez Mazas. The refined, haughty scion of a wealthy Bilbao family, Sánchez Mazas co-founded the Spanish fascist movement, the Falange. Spain's "first fascist" then devoted all his substantial literary talent to stirring up the mood of reactionary frenzy that, in July 1936, would plunge his country into "a savage orgy of blood". Theoretically - but only theoretically - in love with heroic sacrifice, the drawing-room fascist spent most of his co-conspirator Franco's war in hiding or in custody. Then, as the Republican front crumbled outside Barcelona, he and 49 other high-ranking Nationalist prisoners were marched into the forest for summary execution by government troops.

Ever the cowardly aesthete, Sánchez Mazas scarpers into the trees, where a Republican regular finds him in a ditch. In a mysterious deed of mercy, the "Red" soldier gazes at him, then turns away, saving a life with a look of "secret or unfathomable joy".

Miraculously spared, Sánchez Mazas hides out in the woods, protected by Catalan peasants who know the war is lost and treat their succour to this famous Falangist as a long-term insurance policy. (He does keep his word to them later, interceding to spring family members from jail.)

After the Nationalist victory, Sánchez Mazas briefly becomes Minister without Portfolio. He can't be bothered to attend Cabinet meetings, and retires to write fanciful novels expressing the romantic, neo-feudal world-view - Cercas cleverly dubs it "Pre-Raphaelite" - that Franco's regime would soon water down into "sanctimonious, predictable, conservative slop". This turns out to be the history of a vain, lazy and fortunate man who, without a trace of cruelty himself, abetted the slaughter or persecution of millions of fellow-citizens.

Javier's lover Conchi (a fun-loving but shrewd TV fortune-teller) hates the idea of her "intellectual" boyfriend cosying up to the ghost of a posh fascist. And so, initially, does the reader. The opening third of the novel wittily, sometimes farcically, shows how Javier slides into an obsession with his "true tale". Then comes the historical meat in this subtle fictional sandwich, as he unfolds Sánchez Mazas's escape and survival from the Falangist's perspective.

Disturbingly, we end up rooting for this toxic far-right ideologist as he dodges Republican patrols, skulks in the forest and wins the trust - or at least silence - of local farmers. In this book about myth-making and misinformation, Cercas demonstrates how Sánchez Mazas himself exploited his adventure: the single slice of danger in a pampered life.

If Soldiers of Salamis ended with the death in 1966 of this "antiquated gentleman", it would count as an intriguing piece of revisionism that proved just how far Spanish writers had come from the anti-fascist pieties of the immediate post-Franco period. But the last third transforms an ingenious book into a moving, important one. We return to the comic tone of the first section, as it dawns on Javier that the key to his account lies not with Sánchez Mazas himself but with the vanquished Republican who spared his life. Thanks to some chance recollections from the Chilean-born writer Roberto Bolaño (another "real" person here), Javier decides that he knows the identity of the merciful infantryman, and sets out for an old folks' home in Dijon to find him.

Did the hard-drinking veteran Enrico Miralles really save the skin of the "first fascist", on a passing whim or in some mystical act of altruism? What we do discover beyond doubt is that Miralles spent nine hard years as a tireless warrior for liberty. He battled for democratic Spain against Franco; for the handful of Free French in north Africa against Mussolini; in Normandy and Germany, against Hitler. The novel, much to Javier's and our surprise, has stumbled on a cast-iron modern hero.

Sánchez Mazas himself propagated the fascist myth of the "squad of soldiers" which, like the Athenians at Salamis, "saved civilisation" at the eleventh hour. From the defence of Madrid to the crossing of the Siegfried Line, the boozy, profane Miralles really did belong to that squad - except that he fought for everything the Falangist despised. Our stance shifts again as we sense the texture not of another lie or legend but, amazingly, of solid ground.

Soldiers of Salamis is a fairly short novel, yet it feels, not long, but large: spacious, generous, nuanced. Anne McLean's deft translation captures all its humour, and all its gravity. The Orwell who saluted the "crystal spirit" of solidarity via the figure of a tough militiaman in Barcelona would surely admire, and applaud, it.