The Holocaust was the genocide of approximately six million European Jews during World War II, a programme of systematic state-sponsored murder by Germany, led by Adolf Hitler and the Nazi Party, throughout German-occupied territory. Of the nine million Jews who had resided in Europe before the Holocaust, approximately two-thirds were killed. In particular, over one million Jewish children were killed in the Holocaust, as were approximately two million Jewish women and three million Jewish men.
Some scholars maintain that the definition of the Holocaust should also include the Nazis' genocide of millions of people in other groups, including Romani, communists, Soviet prisoners of war, Polish and Soviet civilians, homosexuals, people with disabilities, Jehovah's Witnesses and other political and religious opponents, which occurred regardless of whether they were of German or non-German ethnic origin. This was the most common definition from the end of WWII to the 1960s. Using this definition, the total number of Holocaust victims is between 11 million and 17 million people. Henry Friedlander defines the Holocaust as "the mass murder of human beings because they belonged to a biologically defined group", meaning "the Nazis applied a consistent and inclusive policy of extermination only against three groups of human beings: the handicapped, Jews, and Gypsies.."
The persecution and genocide were carried out in stages. Various laws to remove the Jews from civil society, most prominently the Nuremberg Laws, were enacted in Germany years before the outbreak of World War II. Concentration camps were established in which inmates were subjected to slave labor until they died of exhaustion or disease. Where Germany conquered new territory in eastern Europe, specialized units called Einsatzgruppen murdered Jews and political opponents in mass shootings. The occupiers required Jews and Romani to be confined in overcrowded ghettos before being transported by freight train to extermination camps where, if they survived the journey, most were systematically killed in gas chambers.
Every arm of Germany's bureaucracy was involved in the logistics that led to the genocides, turning the Third Reich into what one Holocaust scholar has called "a genocidal state".