In 1968, the French politician Pierre Mendès France was interviewed for the film The Sorrow and the Pity. Mendès France – who had escaped from a Vichy prison to join the Free French air force – described what he took to be the absurdity of the spirit in which the last governments of the Third Republic approached military matters before the defeat of 1940, which ended that republic. For Mendès France, this spirit was exemplified by the fact that a group of ‘well-meaning bourgeois ladies from Paris’ had raised money to pay for the planting of roses along the Maginot Line – the fortifications on France’s eastern frontier – so that its concrete bunkers would seem more cheerful to the soldiers who served there.

Like Mendès France, many writers have treated the Maginot Line as a subject of bitter humour. It is often held to symbolise an obsession with defensive warfare that sprang from horror at the high casualties of the First World War. It seemed to have served no purpose because it defended the frontiers with Germany and Italy but left the border with Belgium unprotected. It was through neutral Belgium that the Wehrmacht passed in May 1940. Condemnation of the Maginot Line often went with more general criticism of the prewar political order. The man who was to dominate postwar France, Charles de Gaulle, was an advocate of mobile warfare. After 1945, Gaullists took the Maginot Line as a symbol of everything that had been wrong with France. Among theorists of war, the Maginot Line epitomised irrational attachment to an obviously flawed strategy.

Kevin Passmore’s important and deeply researched book offers a different perspective. He is sceptical of interpretations that present the French defeat of 1940 as a product of national decadence. He points out that the Maginot Line did not imply an unthinking faith in defensive warfare. French strategists understood that the