The Holocaust was also conducted under the auspices of racial hygiene. Between 1939 and 1945, Nazis and their collaborators were responsible for the deaths of 11 million to 14 million people, including about 6 million Jews, representing two-thirds of the Jewish population in Europe. Deaths took place in concentration and extermination camps and through mass executions. Other persecuted groups included Poles, communists, homosexuals, Jehovah's Witnesses and trade unionists, among others. Hitler probably never visited the concentration camps and did not speak publicly about the killings.