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World War 2
The First World War set the stage for World War II which broke out two decades later and was more devastating. Adolf Hitler and the Nazi Party signed strategic treaties with Italy and Japan, Hitler’s invasion of Poland in September 1939 made Great Britain and France declare war on Germany. World War II had begun. Over the next six years, the war took more lives than any other war. There were around 6 million Jews killed in Nazi concentration camps, it's now known as the Holocaust.