Just before dawn on 10 May 1940 the largest concentration of motorised vehicles in history roared into action. After months of quiet it was the start of Hitler’s invasion of the West. What followed was a stunning combination of new tactics and new technologies that left Britain and France – two world superpowers - reeling. Within 6 weeks the latter would sign a humiliating armistice, ensuring that almost all of continental Europe had fallen under the grip of Nazi rule. But why did France fall so quickly? In this documentary Dan Snow tells the story of the 6 weeks that led to the Fall of France in 1940 and how its outcome helped shape the course of the 20th century.