Diocletian

Born Diocles around 242 to a low-status family in Dalmatia, he rose through the legions as a cavalry commander until troops proclaimed him emperor in 284 after his predecessor died on campaign in Persia. He stabilized an empire that had been collapsing through the Third Century by dividing power: Maximian took the West in 286, then two junior Caesars joined in 293, creating the Tetrarchy — rule of four. The system worked while he held it together, with successful campaigns against Persia, the Sarmatians, and usurpers, plus a sweeping reorganization of provinces, taxes, and bureaucracy that mad…