During the first half of the twentieth century, nationalizing processes in Europe and Palestine reshaped observant Jewry into two distinct societies, ultra-Orthodoxy and national-religious Judaism. Tracing the dynamics between the two most influential Orthodox political movements of the period, from their early years through the founding of the State of Israel, Daniel Mahla examines the crucial role that religio-political entrepreneurs played in these developments. He frames the contest between non-Zionist Agudat Yisrael and religious-Zionist Mizrahi as the product of wide-ranging social and cultural struggles within Orthodox Judaism and demonstrates that at the core of their conflict lay deep tensions between rabbinic authority and political activism. While Orthodoxy's encounter with modern Jewish nationalism is often cast as a confrontation between religious and secular forces, this book highlights the significance of intra-religious competition for observant Jewry's transition to the age of the nation state and beyond.