The Mobility of Terror: Examining the Decision to Travel or Remain Home in U.S. ISIS Cases from 2014–2025

In 2019, the Islamic State of Iraq and al-Sham (ISIS) was driven out of Syria, marking an official end of nearly five years of its self-described territorial caliphate. During this period, hundreds of Americans travelled or attempted to travel to join ISIS, and foreign terrorist fighter travel has continued since. Other homegrown violent extremists stay home and plan attacks in support of ISIS, such as the New Orleans attack on January 1st, 2025. Little research has compared the decision to travel versus act in the homeland for ISIS-inspired persons, especially after the caliphate’s fall. This study addresses that gap using original data from federal court documents. With original data on over 250 ISIS-affiliated defendants in the U.S. we quantitatively analyze patterns related to intentions to travel versus remain home and compare trends across pre-, active, and post-caliphate periods. Findings show significant differences in the decision to travel alongside the caliphate timeline and highlight limitations in past descriptive research. This study has implications for future research and national security efforts to prevent foreign terrorist fighter travel, offering insights into challenges faced in countering homegrown violent jihadism.