By Rosemary Bailey
Weidenfeld & Nicolson, £18.99

Midnight parachute drops, secret mountain hideouts, coded messages hidden in bread crusts: the tales of derring-do in Rosemary Bailey's latest book would not be out of place in a Boys' Own adventure story.

Indeed, they do provide a certain light relief in this thorough, thought-provoking and at times deeply disturbing account of the impact of the Second World War on the villages and towns of the Pyrenees.

This is Bailey's third book about the Pyrenees, an area she clearly knows extremely well and loves deeply. Despite her knowledge, however, she gradually realised that the region's recent past remained a "veiled history", a period many local people didn't want to discuss with her or even recall for themselves.

Drawing on love letters, archive material, memoirs and extensive interviews with elderly survivors, Bailey has nevertheless pieced together a vivid portrait of a determined, resilient people, actively involved in both resistance and collaboration, responsible for acts of brutality on the one hand, extraordinary courage and selflessness on the other.

From 1939, the Pyrenees found itself on the frontier of two wars, with refugees escaping in both directions. For the next six years, the region experienced an invasion of desperate people from all over Europe. First came the Spanish refugees, in flight from the civil war and Franco; then the French themselves, following the ignominious defeat by Germany in June 1940 and the establishment of the Vichy government; and then, of course, there were the Jews.

There were an estimated 300,000 Jews in France by 1940, almost half of whom were recent immigrants, from Germany, Belgium and Holland. Paris had the third largest Jewish community after Warsaw and New York. After the passing of the infamous Statut des Juifs, in October 1940, their situation changed dramatically for the worse. Thousands fled south to the Pyrenees. Some, like Alma Mahler and her fourth husband, the Czech writer, Franz Werfel, escaped over the mountains into Spain, and from there to America. Others, such as Walter Benjamin, struggled over the mountains only to be turned back at the border. Rather than be returned to France and certain imprisonment, Benjamin killed himself with a massive dose of morphine.

The role of the Vichy government in the rounding up of Jews in France is still a sensitive issue. Bailey, at least, is clear that the French government played an active and enthusiastic part.

French concentration camps, such as Rivesaltes near Perpignan, had been set up originally to contain Spanish refugees but, by the end of 1941, there were an estimated 40,000 Jews in the camps in southern France.

By August 1943, Rivesaltes was the main collection centre in Unoccupied France. Not for nothing was Rivesaltes known as the "Drancy of the South". Conditions were appalling. Many people, children and babies especially, died from hunger, cold, typhus, and gastro-enteritis. Mothers were urged to abandon their children - their best chance of life. Eyewitness accounts of these desperate separations make heartbreaking reading. Those who survived the French camps were deported to Auschwitz, Ravensbruck or Majdanek.

Extraordinarily brave individuals did what they could. Thousands of Jewish children were saved thanks to the tireless efforts of people such as the Quaker Edith Pye, nurses Mary Elmes and Alice Resch, Donald Lowrie, Hiram Bingham, and Varian Fry, sometimes called "The American Schindler". Nevertheless, Bailey's account raises the usual questions about the extent to which relief efforts may have unwittingly colluded in the Final Solution.

The Jews were not the only victims of war in the Pyrenees. Nor were they only victims. Many were actively and effectively involved in the Resistance, fighting alongside Spanish refugees and local people. Ultimately, no one in the region emerged entirely unscathed.

Inspiring in places, horrifying in others, Bailey's portrait of the Pyrenees at war is a quiet triumph of historical reconstruction.

Rebecca Abrams's latest book is Touching Distance (Macmillan)