How long did World War II last?

The story behind the answer

World War II lasted 6 years, from September 1, 1939—when Nazi Germany invaded Poland—to September 2, 1945, when Japan formally surrendered aboard the USS Missouri. In Europe, fighting ended earlier with V-E Day on May 8, 1945, but the global war officially concluded only after Japan’s surrender, marking a full six-year span.

Context: WWII became the largest and deadliest conflict in history, stretching across Europe, Africa, Asia, and the Pacific and reshaping the modern world. Memory tip: think “’39 to ’45”—subtract the first two digits (3 from 9) to get 6, the war’s duration. While some conflicts predated 1939 (e.g., in Asia), the commonly recognized global timeframe is 1939–1945.