Marc Bloch wrote Strange Defeat during the three months following the fall of France, after he returned home from military service. In the midst of his anguish, he nevertheless "brought to his study of the crisis all the critical faculty and all the penetrating analysis of a first-rate historian" (Christian Science Monitor).

Bloch takes a close look at the military failures he witnessed, examining why France was unable to respond to attack quickly and effectively. He gives a personal account of the battle of France, followed by a biting analysis of the generation between the wars. His harsh conclusion is that the immediate cause of the disaster was the utter incompetence of the High Command, but his analysis ranges broadly, appraising all the factors, social as well as military, which since 1870 had undermined French national solidarity.