What does the Garissa attack mean for the fight against ISIS?

The horrifying and lethal Al-Shabab attack on Garissa University this week and its Mogadishu hotel siege last week highlight one of the fundamental difficulties that arise when jihadi movements metastasize from terrorism to insurgency and devolve back again.

Purely terrorist groups, such al-Qaeda before 9/11, are typically small. Insurgencies generally require much more manpower. Taking and holding a given town or a province takes hundreds or thousands of fighters. When a terrorist group adopts an insurgent approach with any degree of success, its ranks typically swell. If the insurgency fails but is not definitively crushed, it can free up potentially thousands of experienced fighters for terrorist activities.

And as Garissa shows, killing civilians requires far fewer people than taking and governing territory. It only takes a handful of fighters to create a tragedy of massive proportions. Even a small insurgency, transformed, makes for a huge terrorist capability.

In light of this, it is critically important that we start thinking now about the fall of ISIS, which commands far more fighters than al Shabab and has encouraged those fighters to even wilder excesses of violence under a more explicitly apocalyptic worldview. Should a coalition dislodge ISIS from its territory, tens of thousands of fighters could potentially be cut loose and re-purposed to terrorism.

It’s imperative that we come up with a strategy to track fighters leaving Iraq and Syria. It’s also desperately important that there be some kind of state structures capable of truly securing ISIS prisoners after its insurgency fails, whether that happens sooner or later. Finally, it is vital that we come up with new approaches to the currently intractable problem of deradicalization. Even imperfect deradicalization programs are preferable to none.

If we fail to get out ahead of this challenge, tragedies like Garissa may pale in comparison to what the future holds. Beating ISIS on the battlefield is only the first step.

This piece originally appeared in Intelwire.