World War 2 began after Germany's defeat in World War 1 led to harsh conditions under the Treaty of Versailles. This created economic instability and paved the way for Adolf Hitler and the Nazis to rise to power in Germany. Hitler began militarizing Germany and conquering neighboring states, joining with Italy and Japan to form the Axis Powers. After Japan's attack on Pearl Harbor, the U.S. entered the war against Germany and Japan. Over 60 million people died during the war before Germany surrendered in 1945 following the Allied invasion of Normandy and the dropping of atomic bombs on Hiroshima and Nagasaki, bringing the war to an end.