Foreign fighters continue to flow into Syria to join the Islamic State group despite its forces being largely decimated, Pentagon Joint Chiefs chairman Joe Dunford said Tuesday.
Even though the jihadist group's territory has shrunk to a fraction of what it once was, new followers arrive, mostly over the Turkish border, at a rate of about 100 a month, Dunford said.
While that is down from a peak of about 1,500 a month three years ago, it shows that Islamic State's ability to attract followers remains potent, he said.
"It's the flow of foreign fighters, the ability to move resources, and the ideology that allows these groups to operate," Dunford said, opening a conference on countering violent extremism.
Dunford also said that the inflow adds to the mounting problem of how to handle hundreds of captured foreign fighters whose home countries will not take them back.
He said the Syrian Democratic Forces are holding more than 700 Islamic State fighters from around 40 countries.
"The progress of returning these fighters home for prosecution has been delayed by political considerations and inconsistent legal frameworks."
Britain, for example, has refused to repatriate the two remaining men of the IS unit dubbed the "Beatles," which kidnapped, tortured and beheaded a number of foreigners including journalists.
London stripped them of their citizenship and has said it does not want them back.
The United States has repatriated one of its IS foreign fighters to stand trial, but has not divulged the fate of any others thought to be held in Syria or Iraq.