The Spanish civil war is staggering to its inevitable conclusion. After the fall of Barcelona, the remnants of the Republican army flee towards the French border. An order comes for them to execute their nationalist prisoners, among them Sanchez Mazas, one of the ideologues whose inflamed rhetoric brought catastrophe to Spain in the first place.

Some 50 of the prisoners are lined up. Mazas hears the shots but, realising he has only been wounded, escapes into the woods. He is discovered by a republican militiaman, who stares him in the face, and then spares his life, shouting to his companions that there is no one there. For several days, the Falange leader hides out in the forests, helped by some deserters from the Republican side, and then is rescued by Franco's troops. He is received as a hero, and feted throughout the newly nationalist country.

He is made a minister in the first Franco government, but quickly becomes disillusioned with the grubbiness of everyday politics, so far from his early high poetic ideals. He inherits money, and lives out his days as a frustrated writer, pursued by dreams of glory and heroism, so lacking in his own life.

Mazas's story is the central panel of Javier Cercas's tryptich. In the first part, we meet the narrator, also called "Javier Cercas", who disarmingly admits from the start that he is a failure as husband and writer. He hears of the story of Sanchez Mazas from the Falangist's son, and the fact that he has just lost his own father sets him on a journey to rescue the forgotten writer from oblivion, in the hope that he might also rescue his own career.

The narrator is fascinated by the way memory congeals into history: the insidious process by which personal narratives become part of a past that can no longer be verified, and is therefore taken to be the truth, even though it is only one possible version of what actually happened. As Cercas points out, the events of the Spanish civil war, which took place only a generation earlier, are becoming as distant and fixed as the story of the soldiers who fought the Persian fleet at Salamis more than 2,000 years earlier.

The narrator is at pains to stress that he is telling a "true story". But from the very outset of Soldiers of Salamis it is plain that this is a literary quest, the hope being that the fictional invention will be more convincing in the end than any biographical memoir. A vital part of the attempt to keep the past as living memory rather than dead history is to investigate individual motives, and the story of Mazas revolves around a central question: what exactly makes a hero? Is it someone like Mazas, who proclaims the glory of violence and the need for radical change, but never actually fights for it; or is heroism something different entirely?

Cercas's response comes in the third section of the novel. This is an account of how the narrator manages to track down the person who might have been the republican militiaman who spared Mazas's life. This man, Antoni Miralles, will not say straight out whether he was the man or not. But talking to him in an old people's home on the outskirts of Dijon, in France, the narrator becomes convinced he is the real hero, "someone who has courage and an instinct for virtue, and therefore never makes a mistake, or at least doesn't make a mistake the one time when it matters, and therefore can't not be a hero".

The book ends with the narrator triumphantly certain that, whether or not Miralles was the man in question, on the level of his own fiction he is the perfect fit to help "complete the mechanism" of his book, and in so doing rescue from oblivion all the "soldiers of Salamis" - the warriors who were heroes despite knowing they were fighting an already lost cause.

Cercas's book has created a sensation in Spain. Whereas in Britain it is easy enough to know who the heroes were - the ones who fought and defeated fascism - the situation in Spain is very different. Not only was the country split in two during the civil war, but there followed 40 years of rule by one side that sought to deny any virtues to its adversaries. As Cercas tells us, "there is a monument to the war dead in every town in Spain. How many have you seen with, at the very least, the names of the fallen from both sides?"

Yet at the same time, Franco and his supporters "won the war but lost the history of literature". Internationally, it is the republicans who are seen as heroes, whether the writer is Hemingway, Orwell or André Malraux. In the end, Soldiers of Salamis remains firmly in this tradition, while offering a gentle and often moving reassertion that individual lives and actions matter most, however overwhelming the historical circumstances may seem.

Nick Caistor is the translator of Juan MarsË's Lizard Tails.

Este libro, que se jacta tanto de no fantasear, de ceñirse a lo estrictamente comprobado, en verdad transpira literatura por todos sus poros. Los literatos ocupan en él un puesto clave, aunque no figuren en el libro como literatos, sino en forma de circunstanciales peones que, de manera casual, disparan en la mente del narrador la idea de contar esta historia, de hacerla avanzar, o la manera de cerrarla. La inicia Sánchez Ferlosio, revelándole el episodio del fusilamiento de su padre, y, cuando está detenida y a punto de naufragar, la relanza Roberto Bolaño, hablando a Javier Cercas del fabuloso Antoni Miralles, en quien aquél cree identificar, por un pálpito que todo su talento narrativo está a punto de convertir en verdad fehaciente en las últimas páginas del libro, al miliciano anónimo que perdonó la vida a Sánchez Mazas. Este dato escondido queda allí, flotando en el vacío, a ver si el lector se atreve a ir más allá de lo que fue el narrador, y decide que, efectivamente, la milagrosa coincidencia tuvo lugar, y fue Miralles, combatiente de mil batallas, miliciano republicano en España, héroe anónimo de la columna Leclerc en los desiertos africanos y compañero de la liberación en Francia, el oscuro soldadito que, en un gesto de humanidad, salvó la vida al señorito escribidor falangista convencido de que, a lo largo de la historia, siempre un pelotón de soldados 'había salvado la civilización'.