The Death and Life of Terrorist Networks

 The Islamic State (or ISIS) is quietly "rising from the ashes" in parts of Iraq and Syria, but this is not the first time that it has recovered from a near-death experience. Its predecessor, al Qaeda in Iraq, also reconstituted itself after nearly being defeated in 2007–8. ISIS has demonstrated extraordinary resilience; about half of all terrorist organizations fail in their first year, but it has survived for the better part of two decades despite fighting against an international coalition assembled to defeat it.

This resilience may seem surprising, but it should not. Over recent decades, militant groups with the kind of vast international network of affiliates, allies, and supporters that ISIS has assembled have proved difficult to defeat. Alliances have helped ISIS expand and gain influence in good times and have relieved pressure by deflecting attention toward affiliates in bad times....