At the start of World War II, France was still a world power. The U.S. and many other nations were relying on the French, along with their ally Britian, to stop Hitler. But in just 6 weeks in May and June 1940, the Germans conquered France, Belgium, and The Netherlands; and drove the British off of continental Europe. The incredibly swift German victory completely changed the balance of power in the world; and woke up the isolationist United States.