To come back to the original q'n, if Turkey were to be attacked, we are obliged to help, that being a core principle of NATO and not negotiable. But IS hasn't attacked them nor is there any sign of them doing so. Turkey clearly has it's own priorities and seems to hate Assad more than IS; their list of demands reflects this. The no-fly zone they've demanded, for instance, can only help IS. I don't see we're obliged to attack Syria just to make Turkey happy.