Germany implemented the persecution of the Jews in stages. Following Adolf Hitler's appointment as German Chancellor in January 1933, the regime built a network of concentration camps in Germany for political opponents and those deemed "undesirable", starting with Dachau on 22 March 1933. After the passing of the Enabling Act on 24 March, which gave Hitler plenary powers, the government began isolating Jews from civil society, which included a boycott of Jewish businesses in April 1933 and enacting the Nuremberg Laws in September 1935. On 9–10 November 1938, during Kristallnacht (the "Night of Broken Glass"), Jewish businesses and other buildings were ransacked, smashed or set on fire throughout Germany and Austria, which Germany had annexed in March that year. After Germany invaded Poland in September 1939, triggering World War II, the regime set up ghettos to segregate Jews. Eventually thousands of camps and other detention sites were established across German-occupied Europe.