Both countries had fought each other for four years in 1914-1918, with France successfully resisting Germany at every turn of battle along the Western Front during World War I. Shirer, who knew French, did much of his own research for his 1969 book by speaking with surviving politicians and French leaders from the immediate prewar period as well as those who were on duty during the final catastrophe.

Although it was desperately important for France to match its enemy's traits with determination and unity of its own, French national leaders instead frittered away their final months before the catastrophe in a round of internal hostility, intrigue and backbiting, which led to the restoration of World War I hero Marshal Philippe Pétain as prime minister.

The German Blitzkrieg defeated the French Army and France's will to fight and resist the invaders.

Key leaders and politicians, led by the aging Pétain and the corrupt, power-hungry Pierre Laval, stepped in and proclaimed their devotion to the survival of France within a Hitlerian New Order for Europe.

Overawing the French Parliament, which had fled occupied Paris and was meeting in exile in the resort town of Vichy, they forced their fellow politicians to grant them full powers to control the remainder of unoccupied France for the remainder of the war.