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.