Diego Gambetta is professor of social theory at the European University Institute, Florence, and official fellow of Nuffield College at the University of Oxford. His books include The Sicilian Mafia and Codes of the Underworld (Princeton). Steffen Hertog is associate professor of comparative politics at the London School of Economics. He is the author of Princes, Brokers, and Bureaucrats.

The violent actions of a few extremists can alter the course of history, yet there persists a yawning gap between the potential impact of these individuals and what we understand about them. In Engineers of Jihad, Diego Gambetta and Steffen Hertog uncover two unexpected facts, which they imaginatively leverage to narrow that gap: they find that a disproportionate share of Islamist radicals come from an engineering background, and that Islamist and right-wing extremism have more in common than either does with left-wing extremism, in which engineers are absent while social scientists and humanities students are prominent. Searching for an explanation, they tackle four general questions about extremism: Under which socioeconomic conditions do people join extremist groups? Does the profile of extremists reflect how they self-select into extremism or how groups recruit them? Does ideology matter in sorting who joins which group? Lastly, is there a mindset susceptible to certain types of extremism? Opening up markedly new perspectives on the motivations of political violence, Engineers of Jihad yields unexpected answers about the nature and emergence of extremism.