This study evaluates whether surprise and intelligence failure leading to mass casualty terrorism are inevitable. It explores the extent to which four factors failures of public policy leadership, analytical challenges, organizational obstacles, and the inherent problems of warning information contribute to intelligence failure. The study applies existing theories of surprise and intelligence failure to case studies of five mass casualty terrorism incidents: World Trade Center 1993; Oklahoma City 1995; Khobar Towers 1996; East African Embassies 1998; and September 11, 21.