Sentence:  His imperial reorganization saw authority divided between four rulers, the <WSD>Tetrarchy</WSD>, to oversee the recovery. 
Meaning of the word marked with <WSD> tags:  A government where power is shared by four people, "especially"  the Herodian tetrarchy established in Judea after the death of Herod and the Tetrarchy of Diocletian which ruled the Roman Empire in the years 293-313.