Battlefield success against ISIS may produce more terrorism for the West, FBI Director James Comey warned this week.

Speaking to a cybersecurity conference at Fordham University Wednesday, Comey predicted that eventually crushing ISIS in its self-proclaimed caliphate in Syria and Iraq will likely result in dispersing terrorists elsewhere.

“At some point there is going to be a terrorist diaspora out of Syria like we’ve never seen before,” Comey said. “Not all of the Islamic State killers are going to die on the battlefield.”

The FBI director’s warning that the collapse of the caliphate will mean increased attacks in Western Europe and the United States mirrors a consensus among intelligence officials.