Out of compulsion but sometimes by choice, the Jews tended to live among themselves and were often brutally herded into ghettos. As the victims of large-scale animosities and cruelties, the Jews learned to be mobile (hence such trades as jeweler, peddler, pawnbroker, and salesman); they developed a rich tradition of parable and an often self-mocking and emotion-relieving humor, but above all they developed a will to survive as individuals and as a people. The culmination of their persecution was the European Holocaust of 1939-45, in which about six million European Jews were systematically murdered and cremated by Nazi Germany.