Less than 20 years after the Great War came to an end, World War II began. America wanted none of it. Opinion polls showed 9 out of 10 agreed with American aviation pioneer Charles Lindbergh:
We believe in an independent destiny for America. ... American boys will not be sent across the ocean to die.
Aviator Charles Lindbergh
Those numbers reversed on December 7, 1941, when the Japanese bombed the U.S. Navy at Pearl Harbor, Hawaii. But America's previous ardent isolationism meant the country was wholly unprepared for war. The next two years would be spent catching up.
Soldiers in 1939:
Pearl Harbor, December 7, 1941
At the start of 1944, Europe was still under the thumb of Nazi Germany. But by the spring of that year, the Allies had gathered enough men and equipment in England for an assault on Germany's "Fortress Europe."
The areas in red were under German control in the spring of 1944.