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date: 20 March 2023


, Roman emperor


, Roman emperor
  • Raymond Davis


Diocletian (Gaius Aurelius Valerius Diocletianus), originally named Diocles. Of obscure origins, born in Dalmatia perhaps in the early 240s ce, he rose to command the domestici (bodyguard) of the emperor *Numerianus on the Persian campaign of 283–4. When Numerianus was killed by his praetorian prefect Aper, the army proclaimed Diocles Augustus at *Nicomedia (20 November 284); he killed Aper. He campaigned (285) against Numerianus' brother Carinus, who was killed at Margus. A usurper Iulianus was also removed, and Diocletian was sole emperor. Visiting Italy, he proclaimed his comrade-in-arms *Maximian as Caesar and sent him to suppress the *Bacaudae. Maximian was made Augustus (286) and spent the next years defending Gaul. Diocletian spent most of his reign on the Danube or in the east. In 287 he installed Tiridates III as king of Armenia and reorganized the Syrian frontier. He campaigned on the Raetian frontier (288); he fought the Sarmatians (285 or 289), and the Saracens (290).


  • Late Antiquity
  • Roman History and Historiography

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