The Holocaust refers to the Nazi campaign during World War II to exterminate the Jewish population in Europe, nearly 6 million Jews were killed. Once in power, the Nazis implemented racist policies outlined by Hitler and persecuted not only Jews but also Roma, Slavs, the disabled, and opposition groups. The Nuremberg Laws stripped Jews of their rights and freedoms. Kristallnacht in 1938 saw coordinated attacks against Jews and synagogues across Germany. Many Jews tried to flee but few countries would accept Jewish refugees due to immigration quotas and anti-Semitism. The Nazis eventually implemented the "Final Solution" to systematically murder Jews and others in concentration and death camps.