The Global Spread of Islamism and the Consequences for TerrorismTerrorism motivated by Islamist religious ideology has been on the rise for the last forty years. Why? The three prior waves of terrorismanarchist, nationalist, and Marxistarose 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