Our understanding of both Jewish history and the history of Western civilization is deepened by this finely balanced account of Christian missionizing among the Jews. Arguing that until the thirteenth century Western Christendom showed little serious commitment to converting the Jews, Robert Chazan proceeds to detail the special circumstances of that critical century in European history. The Roman Catholic Church, characterized at that time by a remarkable combination of vitality and confidence on the one hand and deep-seated insecurities on the other, embarked on its first vigorous campaign to convert the Jews in significant numbers. Chazan examines the new missionizing endeavor in its formative stages, roughly from 1240 to 1280, and analyzes Christian efforts to convince Jews of the truth of Christianity and, at the same time, of the nullity of the Jewish religious tradition. At least as interesting is his investigation of the Jewish lines of response. These ranged from the postures adopted in public debate to the reassurances penned by Jewish leaders for the eyes and ears of their followers only. Although few Jews were converted by the first wave of this new missionizing thrust, it ranked high among the developments that eventually sapped the strength of late medieval European Jewry.