1) Hitler became the leader of Germany in the 1930s and blamed Jews for Germany's problems, believing in extreme anti-Semitism. 2) In 1939, Hitler invaded Poland starting World War 2, and in 1941 Japan attacked Pearl Harbor bringing the US into the war. 3) During the war, over 15 million Americans joined the armed forces and resources were rationed to support the war effort. 4) The Nazis systematically killed over 6 million Jews in concentration camps during the Holocaust.