Persecutions in the seventeenth century are of rarer occurrence than in former times. The most serious one was that which, with several interruptions, lasted from 1648 to 1655, and the leader of which was the Cossack captain Chmelnicki. The Cossacks, who were under the sovereignty of the Polish king, rebelled against their masters, and the Jews had to suffer, partly because they were unable to protect themselves, and partly because, as tax-farmers, they had been the instrument of the extortion practised by the Polish nobles. Thousands were massacred, and since that time the 20th of Sivan is observed as a fast-day in Poland. They fled in all directions, and many great Talmudists among them became rabbis in Western Europe. The Jesuits in Poland and in those places where the Catholic Church had succeeded in crushing the Reformation became very powerful and fostered hatred of the Jews, often resulting in mob violence. In 1664 such a massacre occurred in Lemberg. The Jews were accused of the murder of Christians; similar charges were often made. In 1659 two prominent Jews were put to death on Rosh Hashanah in Rossieny, Lithuania, under the charge of ritual murder; in 1694 Lazarus Abeles and a friend of his were imprisoned in Prague, charged with having killed the son of Abeles, who wanted to become a Christian. Abeles hanged himself and his friend was cruelly put to death. In Vienna and Prague mission services, which the Jews were compelled to attend every Sabbath, were held by the Jesuits since 1630. In 1670 Emperor Leopold I expelled the Jews from Vienna, influenced partly by the hatred of the citizens and partly by the bigotry of the Empress, a Spanish princess. Some of the refugees were given permission by the Elector Frederick William of Brandenburg to settle in Berlin. At about the same time Halle, Halberstadt and Dessau were opened to them. In 1670 Herz Levi of Metz was accused of having murdered a Christian child and was put to death. His innocence was afterwards proved. Peculiar to the history of the seventeenth and eighteenth centuries were the court Jews, Hof-Jude, Hof-factor, Minister-Resident. Prominent among them were Elijah Gomperz of Cleve, Moses Benjamin Wolf of Dessau, Jost Libman of Berlin, Behrendt Lehman of Dresden, and Samuel Oppenheimer and Samson Wertheimer of Vienna. These Jews did service as jewelers, bankers, general brokers and army contractors, and, as such, were exempt from Jewish taxes and certain disabilities. They possessed great influence, which they used to good advantage for their fellow-Jews. Samuel Oppenheimer, who died in 1703, obtained from Emperor Leopold an order of confiscation of an anti-Jewish book, “Entdecktes Judenthum,” by J. A. Eisenmenger (1700), which, up to date, has served as a repertory for anti-Semitic writers.