Since September 11, 2001, 26 jihadist plots and attacks have targeted the American homeland, but because the details of the plots and attacks as well as the profiles of their perpetrators vary greatly, scholars, government officials, and other authorities still disagree about the seriousness of threat posed by jihadist terrorism to the United States. This study provides a clearer understanding of the nature of jihadist terrorism in the U.S. by examining all 26 plots and attacks in detail. It concludes that jihadist terrorism is generally a minimally threatening, homegrown phenomenon, but some plots and attacks still emerge that do pose a serious threat to U.S. national security.
Of the 26 plots and attacks since 9/11, seven can be considered "serious," and the emergence of these plots and attacks can best be explained by examining those using explosive devices separately from those using firearms. Regarding the first category, Western jihadists' contacts with veteran jihadist organizations (such as al-Qaeda) and access to training camps explain the ability of some to construct serious bombing plots. As for the second category, the radicalization of individuals with criminal or military experience accounts for the preparation (and even execution) of serious shooting plots. As a result, the critical point at which a would-be bomber becomes a serious threat is his initial contact with a jihadist group, whereas the critical point for a would-be shooter is his radicalization. Understanding this distinction will allow security services to have a clearer and more nuanced picture of the jihadist threat to the U.S.