How long was World War II ?

World War II lasted 6 years. The war started in September of 1939, with Germany invading Poland. It was ended 6 years later in 1945, also in September.

In May, 1945, Germany surrendered after several losses and Hitler's suicide. The final surrender came from Japan in September, 1945, following the drop of the atomic bombs on Hiroshima and Nagasaki, where nearly 100,000 people died.

World War II was the longest of the two World Wars, and had the most casualties on both sides. Its aftermath was also much longer, and took many more supplies and resources to recover from.