305
A marble head of Diocletian from Nicomedia, now in the Istanbul Archaeology Museums.Image: Dosseman · CC BY-SA 4.0politics · Middle East
Diocletian gives up the Roman throne
On 1 May 305 the emperor Diocletian stepped down at a ceremony outside Nicomedia, in what is now north-west Turkey, while his co-emperor Maximian did the same at Milan. He was the first Roman emperor to give up power of his own free will. Galerius and Constantius became the senior emperors, and Diocletian retired to his great palace on the Dalmatian coast, around which the city of Split later grew.
Source: Encyclopedia.com: Diocletian ↗
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