Anyway, leaving Israel out of this just for a moment or two although I really don't see the Balfour declaration as a legitmate source of legal jurisdiction, the question, I think, here, is who the biggest problem is.

Is Assad, backed by and therefore controlled by Russia the greatest threat to the world, or is it Daish?

It seems to me that the legitimation of a theocracy would be disastrous for the world. At least the Assad regime is notionally secular. So the least bad option (if achievable) is to wipe out all of the wannabee theocrats and then try to mitigate the vileness of the Assad regime.