 Upon arrival, he had established the "Beth Midrash ha-Gadol d'Paris" Talmudic academy where one of the greatest Karaite authorities, Aaron ben Joseph the Elder, was said to have attended.In 1260, control passed to the Egyptian Mamluks and until 1291 Palestine became the frontier between Mongol invaders (occasional Crusader allies).The conflict impoverished the country and severely reduced the population.