"The Holocaust, also referred to as the Shoah, was a genocide during World War II in which Nazi Germany, aided by its collaborators, systematically murdered some six million European Jews, around two-thirds of the Jewish population of Europe, between 1941 and 1945. Jews were targeted for extermination as part of a larger event involving the persecution and murder of other groups, including in particular the Roma and ""incurably sick"", as well as ethnic Poles and other Slavs, Soviet citizens, Soviet prisoners of war, political opponents, gay men and Jehovah's Witnesses, resulting in up to 17 million deaths overall. Germany implemented the persecution in stages. Following Adolf Hitler's rise to power in 1933, the government passed laws to exclude Jews from civil society, most prominently the Nuremberg Laws in 1935. Starting in 1933, the Nazis built a network of concentration camps in Germany for political opponents and people deemed ""undesirable"". After the invasion of Poland in 1939, the regime set up ghettos to segregate Jews. Over 42,000 camps, ghettos, and other detention sites were established. The deportation of Jews to the ghettos culminated in the policy of extermination the Nazis called the ""Final Solution to the Jewish Question"", discussed by senior Nazi officials at the Wannsee Conference in Berlin in January 1942. As German forces captured territories in the East, all anti-Jewish measures were radicalized. Under the coordination of the SS, with directions from the highest leadership of the Nazi Party, killings were committed within Germany itself, throughout German-occupied Europe, and across all territories controlled by the Axis powers. Paramilitary death squads called Einsatzgruppen in cooperation with Wehrmacht police battalions and local collaborators murdered around 1.3 million Jews in mass shootings between 1941 and 1945. By mid-1942, victims were being deported from the ghettos in sealed freight trains to extermination camps where, if they survived the journey, they were killed in gas chambers. The killing continued until the end of World War II in Europe in May 1945."