[1][2] The book focuses on the causes of the French defeat in the Battle of France in 1940, and in part uses a relatively long-term view similar to that in his history scholarship (see Annales school).

The main thesis of the book is that the French leadership failed to recognize that, since World War I, "the whole rhythm of modern warfare had changed its tempo.

"[citation needed] There are only three chapters: Presentation of the Witness, being a short personal history of a life devoted to historical study and interrupted by World War I; One of the Vanquished Gives Evidence, a factual account of his experience in the battle of France; and A Frenchman Examines His Conscience, a biting analysis of the thinking and actions of the generation in the interwar period.

Carole Fink argues that Bloch blamed the ruling class, the military and the politicians, the press and the teachers, for a flawed national policy and a weak defense against the Nazi menace, for betraying the real France and abandoning its children.

Bloch reports a harsh and forthright view of the cause of the defeat as he and fellow officers saw it at the time (p. 20 of the printed French edition, p. 45 of the manuscript, written between July and September 1940): "[W]hatever the deep-seated cause of the disaster may have been, the immediate occasion was the utter incompetence of the High Command.