But in the end, I settle on one very simple reason: We go there so that they don’t come here.

It really is that simple. We bring the fight to the enemy so that they don’t bring it to us. There is a common misconception that if we just let them fight their own wars they will leave us alone. This is wildly untrue for two main reasons. First, groups such as the Islamic State will always try to attack the homeland. And second, even if we manage to prevent them from attacking the homeland, we cannot stop the cascade effect of instability and chaos that ensues when the United States leaves a power vacuum.

Let’s expand on these points. The notion that if we just left these regions alone, they would therefore leave us alone, is at best naive. Consider Osama bin Laden. What exactly did we do to make him hate us? We supported his mujahideens’ cause against the Soviets in the 1980s, and we defended his homeland of Saudi Arabia from Iraqi invasion in the 1991 Gulf War. And yet he planned the 9/11 attacks from Afghanistan, precisely the sort of ungoverned territory that the administration now wants to create in Syria. He hated us because he fundamentally hated Western civilization. The Islamic State and Hezbollah are no different.