World War II (1939–1945) was the deadliest conflict in human history, involving over 30 countries and resulting in 70–85 million deaths. The war began with Nazi Germany's invasion of Poland and expanded to span Europe, Asia, Africa, and the Pacific. Key events include the Holocaust (6 million Jews murdered), the Battle of Stalingrad, D-Day, the atomic bombings of Hiroshima and Nagasaki, and the fall of Berlin. The war ended with the defeat of the Axis powers and led to the creation of the United Nations, the beginning of the Cold War, decolonization of Asia and Africa, and the emergence of the US and USSR as superpowers.