Research brief: How plots come to fail or to be foiled is of great importance to the study of terrorism and to the development of counterterrorism policy. There can be no comprehensive picture of the threat without analyzing what adversaries planned to do as well as what they actually managed to accomplish. Examining failed and foiled plots is essential to understanding their intentions as well as their capabilities. This specific project, “Comparing Failed, Foiled, Completed and Successful Terrorist Attacks,” examines jihadist plots in the United States (121 plots) and selected allied countries (314 plots) occurring between 1993 and 2017. The full report can be found here: START Report to DHS failed and foiled jihadist plots, December 2017.