The span of Rabbi Jehiel Jacob Weinberg's life (1884-1966) illuminates the religious and intellectual dilemmas that traditional Jewry has faced over the past century. Rabbi Weinberg became a central ideologue of modern Orthodoxy because of his positive attitude to secular studies and Zionism and his willingness to respond to social change in interpreting the halakhah, despite his traditional training in a Lithuanian yeshiva. But Weinberg was an unusual man: even at a time when he was defending the traditional yeshiva against all attempts at reform, he always maintained an interest in the wider world. He left Lithuania for Germany at the beginning of the First World War, attended the University of Giessen, and increasingly identified with the Berlin school of German Orthodoxy. Although initially an apologist for the Nazi regime, he was soon recognized as German Orthodoxy's most eminent halakhic authority in its efforts to maintain religious tradition in the face of Nazi persecution. His approach, then and in his later halakhic writings, including the famous Seridei esh, derived from the conviction that the attempt to shore up Orthodoxy by increased religious stringency would only reduce its popular appeal. - Using a great deal of unpublished material, including private correspondence, Marc Shapiro discusses many aspects of Weinberg's life. In doing so he elucidates many institutional and intellectual phenomena of the Jewish world, a number of which have so far received little scholarly attention: the yeshivas of Lithuania; the state of the Lithuanian rabbinate; the musar movement; the Jews of eastern Europe in Weimar Germany; the Torah im Derekh Eretz movement and its variants; Orthodox Jewish attitudes towards Wissenschaft des Judentums; and the special problems of Orthodox Jews in Nazi Germany. Throughout, he shows the complex nature of Weinberg's character and the inner struggles of a man being pulled in different directions. Compellingly and authoritatively written, his fascinating conclusions are quite different from those presented in earlier historical treatments of the period.