The Holocaust was the murder by Nazi Germany of six million Jews. While the Nazi persecution of Jews began in 1933, the mass murder was committed during WWII. The background of the Holocaust was in the prevalent anti-Semitism in Europe and Auschwitz did not begin in Auschwitz. In many cases existing anti-Semitism inhibited people from coming to the aid of the Jews. So it was that very few stood up for the Jews and in four and half years Germans and their accomplices murdered six million Jews. They never showed any restraint and they only stopped when the Allies defeated them.
There was no escape. Not only were Jewish communities destroyed but each Jew was hunted down and traced in order to be put to death. The crime of being a Jew was so great that every single one had to be put to death. They were men, women and children. They were healthy and sick; the committed and the disinterested; the creative and the lazy. There was no reprieve and no amnesty. All of the Jews were meant to suffer and ultimately die. To this purpose industrial scale extermination centers were established.
The Allies finally put a stop to the mass murder. But most of the Jews of Europe had perished by 1945 and a civilization that has flourished for 2000 years was no more.