Original: But from 944 to 947 the realm was plunged into crisis by the revolt of Abu Yazid , who had united the Kharijite Berber tribes of the Aurès Mountains of eastern Algeria and overrun Ifriqiya .
Simplified: But from 944 to 947 there was a crisis by the revolt of Abu Yazid , who had united the Kharijite Berber tribes of eastern Algeria and overrun Ifriqiya .