The 9/11 attacks thus gave the misleading impression that the rise of Islamist extremism was “about” the West and required the West to fight a war on terror in order to defeat it. But Islamist extremism is about Islam and about the regimes that rule in the name of the faith; it is hard to imagine the extremist narrative losing its appeal unless and until Arab regimes gain real legitimacy in the eyes of their own citizens. Alternatively, the very act of setting up a protostate, as the Islamic State has done, may expose the jihadi ideology to expectations of effectiveness it cannot possibly satisfy, so that the radical vision will collapse of its own contradictions, as communism eventually did.
There is a great deal that the West can, must, and will do to defend itself from the terrible consequence of this struggle inside another civilization. Much of that will come under the heading of “homeland defense” — police work, intelligence, border security, and the like. Some will involve rethinking national policies on the treatment of Muslim immigrants. And some, but not much, will involve the use of force abroad. The United States and Europe cannot afford to allow the Islamic State to consolidate its control over territory any more than neighboring states can; it would be absurd to gamble that a Wild West nation of fanatics will not seek to destroy other Islamic regimes and kill all those they deem apostates. The actual fighting, however, will have to be done by Iraqis, Syrians, and other local forces.
The West can defend itself, but there’s little it can do to change the terms of that struggle..’