World War 2 was a global war that involved the majority of the world's nations. Adolf Hitler attempted to take over Western Europe and the Soviet Union with the help of allies Mussolini and Tojo. The war included new tactics like paratroopers and major events like the Japanese attack on Pearl Harbor that brought the US into the war, the D-Day invasion of Normandy, and the Battle of Iwo Jima, a pivotal battle in the Pacific campaign. Key leaders during this time included Hitler, Stalin, Mussolini, and US President Franklin D. Roosevelt.