The Cato Institute’s Chris Preble calls it right.
Simply put, a full-scale ground war with U.S. troops doing most of the fighting isn’t necessary. ISIS currently presents, at worst, a minor and manageable threat to U.S. security. The group has many enemies, and they are growing more determined to resist it by the day. If ISIS expands the territory under its control, it will acquire even more enemies. If it attempts to consolidate control in the territory it already has, it will engender resistance and opposition, as al Qaeda did in western Iraq in 2006.
There is a military mission available—targeted air strikes against ISIS extremists, and military assistance to Kurdish and Iraqi forces taking the fight to them on the ground—that can degrade ISIS’s capabilities, and complicate its now very limited ability to attack the United States. The president should focus upon that narrow mission, and resist the calls to launch the U.S. military on yet another quixotic nation-building crusade in the Middle East.