Daesh's last stronghold is hanging by a thread. The Syrian town of Bukamal near the Iraqi border is all that remains of the terror group's urban territory. This past week, the Syrian regime said they'd liberated it, before the group managed to claw it back. But its collapse appears imminent, and with it, their form of statehood that once held vast expanses of territory across Iraq and Syria. So what comes next? Who fills the vacuum? And what's being done to ensure they don't return?