Shocked by the fall of France in 1940, panicked US leaders rushed to back the Vichy government-a fateful decision that nearly destroyed the Anglo–American alliance. According to US Secretary of War Henry Stimson, the "most shocking single event" of World War II was not the Japanese attack on Pearl Harbor, but rather the fall of France in spring 1940. Michael Neiberg offers a dramatic history of the American response-a policy marked by panic and moral ineptitude, which placed the United States in league with fascism and nearly ruined the alliance with Britain. The successful Nazi invasion of France destabilized American planners' strategic assumptions. At home, the result was huge increases in defense spending, the advent of peacetime military conscription, and domestic spying to weed out potential fifth columnists. Abroad, the United States decided to work with Vichy France despite its pro-Nazi tendencies. The US–Vichy partnership, intended to buy time and temper the flames of war in Europe, severely strained Anglo–American relations. American leaders naively believed that they could woo men like Philippe Pétain, preventing France from becoming a formal German ally. The British, however, understood that Vichy was subservient to Nazi Germany and instead supported resistance figures such as Charles de Gaulle. After the war, the choice to back Vichy tainted US–French relations for decades. Our collective memory of World War II as a period of American strength overlooks the desperation and faulty decision making that drove US policy from 1940 to 1943. Tracing the key diplomatic and strategic moves of these formative years, When France Fell gives us a more nuanced and complete understanding of the war and of the global position the United States would occupy afterward.