The Holocaust was when Adolf Hitler ruled Nazi Germany (known as the Third Reich) during World War II. He used fear to rule over a lot of Europe. Hitler thought that some groups, especially Jewish people, were not as good as others. So he killed and imprisoned lots of innocent people. The German secret police (Gestapo) closely monitored ordinary people. People who wanted to speak out against this did not because they were afraid of the Nazis. Hitler murdered about 6 million innocent Jewish people.