This is exactly what I predicted years ago, i.e. the war in Syria would create huge problems for everyone not least when thousands of these Islamists return to Europe, etc. (I always said that allowing thousands of Islamists to go to Syria to topple the secular Assad govt would result in a massive terrorist problem, especially in Europe, whether the Islamists won the war or not.) And of course it's now a big problem for Turkey, which was the main conduit for Islamists traveling to Syria in the first place. It's called blow-back.

The best thing that can happen is that these terrorists are wiped out in Syria. That's why we must cooperate with Russia. Otherwise the Islamists must not be allowed back to their original countries. That's going to be a problem in the future, i.e. identifying and tracking these terrorists. The whole US-Saudi-Turkey-Western regime-change adventure in Syria has turned into a complete cock-up and an utter disaster, especially for the Syrian people.