An ISIS operative traveled across the Syrian border late last year, settled in a Turkish port city, and began work on a mission to sneak jihadis into Europe. 

It has been successful, he said, in an interview near the Turkey-Syria border: "Just wait".

The operative, a Syrian in his thirties with a close-cropped black beard, said ISIS is sending covert fighters to Europe -- as did two smugglers who said they have helped. 

He smuggles them from Turkey in small groups, he said, hidden in cargo ships filled with hundreds of refugees. 

He said the fighters intend to fulfill ISIS's threat to stage attacks in the West. He views this as retaliation for US-led airstrikes against the group that began in Iraq last summer and Syria last fall. 

"If someone attacks me," he said, speaking with BuzzFeed News on condition of anonymity, "then for sure I will attack them back."