Growing reports of massive death tolls are coming out of eastern Syria, where earlier this month, the Shueitat tribe rebelled against ISIS rule, ousting them from several villages and burning an ISIS headquarters to the ground.

Over the weekend, it was reported that some 700 tribesmen had been slain by ISIS in a crackdown over the previous week. Today, the reports suggest 200 more were killed, putting the overall toll at 900.

The massacre is an aberration for ISIS, which has mostly tried to befriend tribal leaders in securing its rule over land that virtually none of their fighters are from.

The falling out with the tribe began when ISIS apparently reneged on a deal with them, arresting several tribesmen on unknown charges. The tribe struck back quickly, and the situation escalated.

The ISIS massacres seem aimed at being an example to warn other tribes against rebelling, though it of course risks fueling further unrest by other tribes if they try to follow it up with more centralization of power. Ultimately, the ISIS caliphate depends on keeping these tribes more or less on board.