The persecution reached a peak in Nazi Germany's Final Solution, which led to the Holocaust and the slaughter of approximately 6 million Jews. Of the world's 15 million Jews in 1939, more than a third were killed in the Holocaust. The Holocaust—the state-led systematic persecution and genocide of European Jews (and certain communities of North African Jews in European controlled North Africa) and other minority groups of Europe during World War II by Germany and its collaborators remains the most notable modern-day persecution of Jews. The persecution and genocide were accomplished in stages. Legislation to remove the Jews from civil society was enacted years before the outbreak of World War II. Concentration camps were established in which inmates were used as slave labour until they died of exhaustion or disease. Where the Third Reich conquered new territory in Eastern Europe, specialized units called Einsatzgruppen murdered Jews and political opponents in mass shootings. Jews and Roma were crammed into ghettos before being transported hundreds of miles by freight train to extermination camps where, if they survived the journey, the majority of them were killed in gas chambers. Virtually every arm of Germany's bureaucracy was involved in the logistics of the mass murder, turning the country into what one Holocaust scholar has called "a genocidal nation."