The time period in which the Islamic State (IS) controlled territory in Syria and Iraq between 2014 and 2019 coincided with the largest groundswell of homegrown jihadist activity in United States history. This unprecedented wave of jihadist activism, which hit its peak between 2014 and 2016, could be measured through several indicators. Senior officials in the Federal Bureau of Investigation (FBI) testified that the Bureau managed, at any given time between 2014 and 2019, 1,000 active investigations into IS supporters throughout the U.S.; at least 239 alleged supporters were charged in U.S. courts. Meanwhile, more than 80 Americans traveled to Syria and Iraq to join IS, and 16 IS sympathizers that remained in the U.S. conducted terrorist attacks that were inspired by or directed by the group. Others provided resources for IS’ global project in different ways, most notably by supporting IS’ online propaganda dissemination and social media recruitment campaigns.
Vidino, Lorenzo; Hughes, Seamus; Clifford, Bennett; Program on Extremism, George Washington University; and National Counterterrorism Innovation, Technology, and Education Center, "The Islamic State in America: After the Caliphate" (2022). Reports, Projects, and Research. 15.