Saint Louis University Professor Thomas F. Madden, author of "A Concise History of the Crusades", claims the Jewish defenders of Jerusalem retreated to their synagogue to "prepare for death" once the Crusaders had breached the outer walls of the city during the siege of 1099. The chronicle of Ibn al-Qalanisi mentions the building was set fire while the Jews were still inside. The Crusaders were supposedly reported as hoisting up their shields and singing "Christ We Adore Thee!" while they circled the fiery complex." However, a contemporary Jewish letter written shortly after the siege does not mention the burning synagogue. But playing on the religious schism between the two sects of Judaism, Arabist S.D. Goitein speculates the reason the incident is missing from the letter is because it was written by Karaite Jews and the synagogue belonged to Rabbinic Jews.