'Working at the intersection of religion, politics, and violence, Nielsen illuminates the role of Islamist clerics in fomenting extremism along their personal path to radicalization. Undergirding his provocative ideas is a dazzling array of methodological tools, from ethnographic work in Egypt's mosques to statistical analysis of jihadist websites, informed by a nuanced understanding of contemporary Islam. Read this book! It is bold, clear, and compelling.' Ron E. Hassner, author of Religion on the Battlefield 'This is a major contribution to a topic that is notoriously difficult to study: violent extremist Islamist groups. By highlighting the academic identities of jihadist clerics, Nielsen not only adopts an innovative approach that is especially engaging for an academic audience, but also illuminates the incentives and behaviors of at least some jihadist clerics. In so doing, the author points to a pathway to jihadism that has been overlooked in academic and policy circles - 'blocked ambition' - or the ways in which exclusion from state-sanctioned or mainstream Islamic circles compels some clerics toward radical ideologies. Nielsen employs cutting edge methods and data to support his claims, including statistical analyses of extensive text and network data from the Internet as well as more in-depth case studies of particular clerics' lives. Nielsen covers enormous quantities of original material and overcomes a common problem in scholarship on jihadism, which tends to focus only on radicalized clerics rather than comparisons with those who operate in the mainstream.' Melani Cammett, Clarence Dillon Professor of International Affairs, Harvard University, Massachusetts 'Richard A. Nielsen's innovative study significantly enriches the literature on jihadism by moving the focus from fighters to preachers. Examining the case of 'digital' Islamic clerics through sophisticated statistical analysis of novel data sets, he tests a theory of 'blocked ambitions' to explain radicalization. This is a methodological breakthrough that opens new avenues for the study of the ideology of militant jihadism. A must-read for social scientists and policymakers alike.' Malika Zeghal, Prince Alwaleed Bin Talal Professor in Contemporary Islamic Thought and Life, Harvard University, Massachusetts 'In this fascinating and rigorous study, Nielsen argues that one of the key factors explaining jihadi radicalization is the lack of economic and academic opportunities. Taking on arguments that focus on Islam and ideology, Nielsen employs sophisticated and cutting-edge text analyses tools to examine the writings and biographies of jihadi clerics. This in-depth study is an excellent contribution to the study of jihadism and radicalism.' Amaney Jamal, Edwards S. Sanford Professor of Politics, Princeton University, New Jersey 'Why do some Muslim clerics radicalize, abandoning the Islamic mainstream in favor of jihadism? To answer this pressing question, Nielsen compiles a stunning array of new data and deploys the most advanced tools in political methodology. His answer is original and compelling: clerics who experience blocked career ambitions are incentivized to radicalize, with deadly implications for the propagation of Islamic terrorism.' Lisa Blaydes, Stanford University, California