According to the United States Holocaust Memorial Museum (USHMM), the country's official memorial to the Holocaust, "The Holocaust was the murder of six million Jews and millions of others by the Nazis and their collaborators during World War II." Of those murdered for being Jewish, more than half were Ashkenazi Polish Jews.
While the term Holocaust generally refers to the systematic mass murder of the Jewish people in Nazi-occupied Europe, the Nazis also murdered a large number of non-Jewish people who were considered subhuman (Untermenschen) or undesirable. Some victims belonged to several categories targeted for extermination, e.g. an assimilated Jew who was a member of a communist party or someone of Jewish ancestry who identified as one of Jehovah's Witnesses.
Non-Jewish Victims of Nazism included Slavs (e.g. Russians, Poles, Ukrainians and Serbs), Romanis (gypsies), French, Belgians, Dutch, Greeks, Italians (after 1943), LGBT people (lesbian, gay, bisexual, transgender, Pansexual, etc); the mentally or physically disabled, mentally ill; Soviet POWs, Roman Catholics, Protestants, Orthodox Christians, Jehovah's Witnesses, Buddhists, Muslims, Spanish Republicans, Freemasons, people of color (especially the Afro-German Mischlinge, called "Rhineland Bastards" by Hitler and the Nazi regime); leftists, communists, trade unionists, capitalists, social democrats, socialists, anarchists, and every other minority or dissident not considered Aryan (Herrenvolk, or part of the "master race") as well as those who disagreed with the Nazi regime.
Taking into account all of the victims of persecution, the Nazis systematically killed an estimated six million Jews and an additional 11 million people during the war. Donald Niewyk suggests that the broadest definition, including Soviet civilian deaths, would produce a death toll of 17 million.
Despite widely varying treatment (some groups were actively targeted for genocide, while others were not), some died in concentration camps such as Dachau and others from various forms of Nazi brutality. According to extensive documentation (written and photographic) left by the Nazis, eyewitness testimony by survivors, perpetrators and bystanders and records of the occupied countries, most perished in death camps such as Auschwitz-Birkenau.