In a Sunday televised address on the San Bernardino shooting and terrorism, President Barack Obama restated his opposition to deploying ground troops in Syria and Iraq to fight ISIS. "That's what groups like ISIL want. They know they can't defeat us on the battlefield," he argued. "ISIL fighters were part of the insurgency that we faced in Iraq, but they also know that if we occupy foreign lands, they can maintain insurgencies for years, killing thousands of our troops and draining our resources, and using our presence to draw new recruits."
This point can seem a little counterintuitive for those not closely watching the Syrian civil war and terrorism abroad. Luckily, Rukmini Callimachi, who has done extensive on-the-ground reporting on Syria for the New York Times, followed up the speech with a great explanation of why Obama — and many counterterrorism experts — believe that a ground war could do more harm than good:
As Callimachi explained, one of ISIS's key beliefs is that reestablishing the caliphate will lead to the apocalypse by provoking an epochal battle with the "infidel" in the heart of the Muslim world.
"After the victory of the Muslims over the infidel, they believe the world is eventually overrun by Gog and Magog, who will be familiar to folks who know biblical literature — basically wild men who will destroy the world," Will McCants, an ISIS expert and the author of The ISIS Apocalypse, told Vox's Zack Beauchamp. "And then we finally get down to the fire-and-brimstone stuff. The universe explodes, and all of the remaining sinners are gathered before God to face judgment at the final hour."
(For more, read Beauchamp's full explainer on ISIS's obsession with the apocalypse.)
So getting into a ground war with ISIS could help the organization push the idea that its prophecy is really coming to fruition and help the group recruit more people from around the world — on top of potentially bogging down the US and other Western powers in a costly ground conflict just like Iraq War did.