the period from 1100–1600. The authors of the study argue that this stems from people blaming Jews for misfortunes and weak rulers going after Jewish wealth in times of fiscal crisis. The authors propose several explanations for why Jewish persecutions significantly declined after 1600: (1) there were simply fewer Jewish communities to persecute by the 17th century; (2) improved agricultural productivity, or, better-integrated markets may have reduced vulnerability to temperature shocks; (3) the rise of stronger states may have led to more robust protection for religious and ethnic minorities; (4) there were fewer negative temperature shocks. (5) the impact of the Reformation and the Enlightenment may have reduced anti-semitic attitudes. In the Papal States, which existed until 1870, Jews were required to live only in specified neighborhoods which were called ghettos. Until the 1840s, they were required to regularly attend sermons urging their conversion to Christianity. Only Jews were taxed to support state boarding schools for Jewish converts to Christianity. It was illegal to convert from Christianity to Judaism. Sometimes Jews were baptized involuntarily, and, even when such baptisms were illegal, forced to practice the Christian religion. In many such cases, the state separated them from their families; the Edgardo Mortara account is one of the most widely publicized instances of acrimony between Catholics and Jews in the Papal States in the second half of the 19th century. According to Mark R. Cohen, during the rise of Islam, the first encounters between Muslims and Jews resulted in friendship when the people of Medina gave Muhammad refuge, among them were Jewish tribes of Medina. Conflict arose when Muhammad expelled certain Jewish tribes after they refused to swear their allegiance to him and aided the Meccan Pagans. He adds that this encounter was an exception rather than a rule. Of the three Jewish tribes of Medina, the Banu Nadir and the Banu Qaynuqa were expelled in the course of Muhammad's rule after suspicion arose in the Muslim leadership that the Jews were planning the assassination of Muhammad. On the other hand, the Banu Qurayza tribe was eliminated by Muhammad in the aftermath of the Battle of the Trench. The tribe was accused of colluding with Meccan enemies during the Meccan siege of Medina and subsequently besieged. When they surrendered, all grown men were executed and women and children were enslaved. Muhammad is recorded as saying that he would expel all Jews and