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 made the state larger and more centralized than ever before. His Edict on Maximum Prices in 301 flopped immediately, and the Diocletianic Persecution he launched in 303 - the empire's largest anti-Christian campaign - failed to stop the religion's spread; within two decades Constantine would make it the preferred faith. Weakened by illness, Diocletian did what no emperor had done before: he abdicated voluntarily on 1 May 305 and retired to his palace on the Dalmatian coast, where he tended vegetable gardens until his death around 311.