It was never realistic to think that the United States could solve the political problems in Iraq and Syriathat ISIL exploited in order to seize territory in the summer of 2014.

The U.S. military couldn’t fix Iraq when it had 170,000 U.S. troops there. It can’t build a broken country from the air, either, or with a few thousand special operations forces on the ground. Lack of planning isn’t the issue. Some problems defy military solutions.

The U.S. military can, however, wreak havoc on a group of individuals guilty of heinous acts against innocent civilians. And U.S. advisers can assist those on the ground who have the most to lose from ISIL’s continued existence. This approach is actually working. A number of ISIL leaders have been killed by U.S. airstrikes, and its control over territory in Iraq and Syria is slipping away.

Americans were appalled by the horrors ISIL perpetrated, and demanded action when ISIL brutally murdered two American journalists. Attacking ISIL with U.S. air power satisfied the human impulse to exact vengeance on some of the world’s most repugnant people. But it avoided the counterproductive on-the-ground presence that locals resent and that Americans can no longer stomach after nearly 15 years of war.

The limited approach also spurred others to act. With U.S. encouragement and assistance, ISIL’s many enemies have slowly but steadily shrank the group’s rump statelet. The sources of revenue that it had exploited — from the resources in the ground to the money it extorted from the people trapped under its brutal rule — are drying up.

Now, with ISIL’s losses mounting, some fear it will return to its roots, organizing or inspiring attacks in the region and beyond. That problem is best handled by the same approaches used against other terrorist organizations over the decades: applying persistent pressure on the group’s leaders, and attacking its ability to attract new recruits and raise funds.

The U.S. military has a role to play here, but killing terrorists doesn’t require placing tens of thousands of U.S. troops into the middle of the Middle East’s ongoing civil wars.