Book excerpt: This book explores the life and thought of one of the most important but least known figures in early Zionism, Nathan Birnbaum. Now remembered mainly for his coinage of the word "Zionism," Birnbaum was a towering figure in early Jewish nationalism. Because of his unusual intellectual trajectory, however, he has been written out of Jewish history. In the middle of his life, in the depth of World War I, Birnbaum left his venerable position as a secular Jewish nationalist for religious Orthodoxy, an unheard of decision in his time. To the dismay of his former colleagues, he adopted a life of strict religiosity and was embraced as a leader in the young, growing world of Orthodox political activism in the interwar period, one of the most successful and powerful movements in interwar central and eastern Europe. Jess Olson brings to light documents from one of the most complete archives of Jewish nationalism, the Nathan and Solomon Birnbaum Family Archives, including materials previously unknown in the study of Zionism, Yiddish-based Jewish nationalism, and the history of Orthodoxy. This book is an important meditation on the complexities of Jewish political and intellectual life in the most tumultuous period of European Jewish history, especially of the interplay of national, political, and religious identity in the life of one of its most fascinating figures.