Speaking at a conference today, FBI Director James Comey warned that the “eventual defeat” of ISIS would be causing a major problem in and of itself, creating a large “terrorist diaspora” throughout the West because “not all of the Islamic State killers are going to die on the battlefield.”

This is a somewhat different presentation of a long-standing problem, and the term “diaspora” is a bit of a misnomer, since the ISIS fighters in question are in great measure from the West in the first place, which is why going back to their countries of origin is not just possible, but comparatively simple.

With Western recruits joining ISIS by the thousands, there has always been concern of what happens when those fighters return home with a bunch of new skills and ties to international terror. The trickle-back would be greatly accelerated, of course, by ISIS being defeated outright.

Comey likened it to the post-Mujaheddin situation in Afghanistan around 1989-1990, which led to the formation of al-Qaeda and a huge influx of seasoned Islamist fighters into conflicts the world over. Comey warned this situation would be “10 times that or more.”

At the same time, Comey sought to assure the conference that Western Europe was a lot more at risk than the US was from this, reflective of the much larger number of recruits from countries like France into ISIS. At the same time, it’s not difficult for a citizen of an EU member nation to visit the US or anyplace else for that matter, meaning this influx is going to be able to go more or less wherever they want.