The plague pandemic which became known as the Black Death killed about one-third of the population of Europe. The plague had been introduced on ships and overland. While some regions remained almost completely unaffected, others lost their entire population. Considering the plague to be divine punishment, the flagellants, who scourged themselves in the hope that this would bring atonement, roamed through Europe. In many places the Jews were persecuted, because people thought that they had poisoned wells and thus unleashed the plague.