How much of a threat are returning jihadists?

A RAND analysis by internationally renowned terrorism expert Brian Michael Jenkins of more than 100 cases found that almost all of the American jihadists who went overseas ended up dead or landed in the same place as Sinh Vinh Ngo Nguyen. Brought down by his trusted confidante, who was really working undercover for the FBI, Nguyen admitted in court that he was trying to get to Pakistan to help train Al-Qaeda fighters. He was sent to prison for 13 years.

“Yes, this does represent a new layer of threat, a new dimension,” says Jenkins. “But given the numbers of it, it’s something that’s manageable. The fact is, most of the people returning to the United States haven’t done anything because they’re arrested.”

The trickle of American recruits to overseas jihadist groups has quickened in recent years with the opening of new—and especially violent—fronts in Syria and Iraq, according to intelligence estimates. President Obama cited the threat those fighters could pose if they return home “trained and battle-hardened” as one reason to launch air strikes against the group known as the Islamic State.