T he declarations had not yet come, but on Aug. 28, 1939, Europe already knew war was on its way. On that day, 75 years ago, the armies that would fight what became World War II had gathered. Just ...

People often describe World War II as beginning in September 1939 when Germany invaded Poland. But Japan and China had already been at war for several years at that point.

World War II, the world's deadliest international conflict, left almost 80 million people dead. Here's what started it and why it ended in 1945.