How Somalia’s Al Shabaab Turned Against Its Own Foreign Fighters

U.S. COUNTERTERRORISM AGENCIEShave long been preoccupied with the threat posed by the recruiting successes of the Somali terrorist group al Shabaab in Western countries. The group has managed to lure hundreds of foreign fighters — including some 40 Americans — to Somalia through online propaganda videos and word-of-mouth in disaffected immigrant communities.

In recent years, however, al Shabaab has turned on the foreign fighters in its own ranks, waging a brutal campaign to purge the perceive...