Few would argue that Washington’s approach to the conflicts in Afghanistan and Iraq has been a success worth emulating. So the most important question now is what can be learned from the failures.

After a decade-plus of war, the lessons for the United States are clear: fight fewer, more traditional wars and fight them more decisively. Above all, avoid getting entangled in the politics of chaotic countries.

ISIS' army has attracted a stream of Western volunteers, but there is no reason to panic about their return home. Some may come back as terrorists, but the danger has been exaggerated, and the United States and the EU know how to handle such problems.