The Global Spread of Islamism and the Consequences for Terrorism

Terrorism motivated by Islamist religious ideology has been on the rise for the last forty years. Why? The three prior waves of terrorism—anarchist, nationalist, and Marxist—arose generally from a combination of geopolitical events and local grievances. This “fourth wave” of terrorism, however, has risen out of a different set of conditions.

Existing analyses of terrorism often consider how terrorist ideologies have evolved or how grievances have changed over time. But these approaches miss...