How dangerous are Domestic Terror Plotters with Foreign Fighter Experience? The case of Homegrown Jihadis in the US

Do Americans who return home after gaining experience fighting abroad in Islamist insurgencies pose a greater risk than homegrown jihadi militants with no such experience? This study looks at the net effect of foreign fighters on domestic plots in the US by disaggregating data from the Jihadi Plots in the West dataset. It finds that the presence of a returnee decreases the likelihood that an executed plot will cause mass casualties. Also, plots carried out with American returnees from Islamist insurgencies abroad decrease the likelihood that a plot will come to fruition. This may be because the presence of a known foreign fighter increases the likelihood of detection and disruption by law enforcement officials. The US as a case study may not be generalizable to other Western countries because of its unique geographic position and its longer experience of prosecuting would-be foreign fighters.