Experts warned that the diaspora of terrorists following Iraqi defeat of ISIS in Mosul presents a series of new threats to Europe and the United States, while testifying before the House Committee on Homeland Security on Thursday.
According to Colin Clarke of the RAND Corporation, ISIS fighters returning to Europe following fighting in Iraq and Syria will either be "disillusioned," "disengaged but not disillusioned," or "operational." All three types will be dangerous because they have the capacity to carry out attacks or radicalize youth in the places to which they return.
"We still understand very little about the radicalization process, what role the internet and social media play in this process, and what policy should be when it comes to monitoring terrorist use of social media," Clarke said. "Congress might consider funding more fusion cells and allocating resources for law enforcement training to deal with the threat from returning foreign fighters."
In addition to the short-term threat posed by defeated ISIS fighters returning home, the United States and Europe need to consider the children of radicalized ISIS members, Robin Simcox of the Heritage Foundation warned. Dealing with this problem could become a long-term issue, he said.
"There are almost 500 children currently in Syria with connections to France. Approximately 150 such children have been born there. There are approximately 80 Dutch children born in the caliphate and as many as 50 from the U.K. How many of these children will end up returning to the West is at present unknowable," he said.
Recent ISIS videos have depicted a training program, nicknamed "Cubs of the Caliphate," that features children beheading prisoners. Additionally, ISIS-trained teens and pre-teens have carried out 34 attacks in seven countries since 2016, Simcox said.
"The reason why they do this is to shock the conscience of the person, so they think that's there's no way of coming back. The thinking is that if you commit and absolutely horrific crime—that totally goes against all the laws of nature—then you are then indoctrinated for life. This creates a massive problem, and I'm not going to pretend we have answers for how to deal with it," said Thomas Joscelyn of the Foundation for Defense of Democracies.
Jocelyn also said ISIS is using the internet to rapidly spread geographically. Although it has lost Mosul, the Caliphate has established "provinces" in many other parts of the world, notably Afghanistan and Pakistan in 2016. Earlier this year, ISIS captured much of the Philippine city of Marawi. The United States should not count the victory in Mosul as a major victory over ISIS just yet, Joscelyn said.
"We likely do not even know how many members the Islamic State has in Iraq and Syria today," he said.