Yes, the Obama administration has made foreign-policy ineptitude its doctrine – from Ukraine to the Middle East. But Harf has something of a point: Ideology is not the only reason that ISIS has won a global following. Consider whom ISIS is targeting in its propaganda efforts: socially disaffected young men from across the world. It tempts them with visions of unrestrained excitement tied to an ordained purpose. This strategy — I’ve described it as Grand Theft Auto in the flesh — is at the core of why so many thousands now march under the ISIS banner. Abu Bakr al-Baghdadi’s global jihad provides ISIS fighters with inspiring theology, but broader social concerns make many young men open to this theology in the first place.

These social concerns are primarily of two sorts. First, there are those (predominantly in North Africa and the Middle East) who are angry at the  endemic corruption and the lack of social mobility in their country; They see ISIS as a path to glory. Then there are those in the West who, imprisoned in poverty and judged for their “otherness,” are wooed by the malevolent charisma of Wahhabi and Salafi clerics. Consider what’s happening in Britain, France, and much of mainland Europe. The social foundations for Salafi-radicalism are clear. Conversely, America’s inclusive national identity means that comparatively few Americans have joined ISIS.