Well, allow me to explain my opinion.
The last months, in the now democratic states of Egypt, Lybia and IIRC Tunisia as well, more radical islamic figures have taken over control. The fighting of radical islamic groups have, for now, been relatively contained in the middle east...
For the next part of reasoning, we need a W-euro country, Belgium for example. In Belgium there are more than a million foreigners. Large amounts of those are muslims. These days, the muslim youth is becoming increasingly intolerant to the native society and its law, but in Belgium, law is a joke. This gave rise to organisations such as Sharia4Belgium. It has been accused of supposed terrorist funding, calling for hate, racism etc. I bet, that's not the only organisation, and we don't know its actual size of members.
Now, you may call me paranoid, but I wouldn't be at all surprised if, when that war would break out, we would also have fighting going on, on our very doorstep, by members of such groups.