Roman Emperor Diocletian (Gaius Aurelius Valorous Diocletianus) was born on 22 December 244.

By Jean Marie Carey

Roman Emperor Diocletian (Gaius Aurelius Valorous Diocletianus) was born on 22 December 244. Growing up in Dalmatia in a non-aristocratic family, Diocletian rose to prominence as bodyguard of the emperor Numerianus during the Empire’s Persian campaign of 283–4. 

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. On 1 March 293 he established the “tetrarchy.” To the two Augusti, now known as Iovius and Herculius respectively to emphasize their quasi-divine authority, were added Caesars, Constantius and Galerius; these were adopted into the Jovian or Herculian houses by the marriage of Galerius to Diocletian’s daughter Valeria and of Constantius to Maximian’s daughter Theodora. The arrangement provided an imperial presence in across the region.

Diocletian was an enthusiast for what he understood of Roman tradition and discipline. He reigned 21 years and then abdicated voluntarily, and spent the remaining years of his life in peaceful retirement. Diocletian was one of the few emperors of the third and fourth centuries to die naturally, and the first in the history of the empire to retire voluntarily. Once he retired, however, his tetrarchic system collapsed. His most visible legacy are the many and far-flung architectural monuments erected during his rule. Diocletian died 3 December 312 at age 67 in the palace he had built in what is now Split, Croatia. 

Reference: “Diocletian.” In The Oxford Classical Dictionary. sOxford University Press, 2012.http://www.oxfordreference.com/view/10.1093/acref/9780199545568.001.0001/acref-9780199545568-e-2187.

Further Reading: Pat Southern. The Roman Empire from Severus to Constantine. London: Routledge, 2015.

Trevor Bryce. Ancient Syria: A Three Thousand Year History. Oxford: Oxford University Press, 2014.


The Four Tetrarchs Under Diocletian and the Tetrarchy, 305. Corner Façade of San Marco, Venice, Italy. Origin Constantinople, appropriated 12th century. Photo: Sara N. James.

Baths of Diocletian, exterior, c. 250, Rome. Photo: David Friedman, Massachusetts Institute of Technology.

Roman Forum – Curia Julia, Rome. Built by order of Caesar, completed by Augustus; restored by Diocletian. (Originally built in 29 BCE; destroyed by fire in 283, and repaired before 311.) The meeting place of the Senate built by Caesar, the Curia Julia, corresponds to the large brick building, in part restored in the modern period, that occupies the entire north side of the small square. The building work, begun by Caesar, was only completed by Augustus in 29 BCE. The current state of the Curia Julia belongs to a restoration carried out by Diocletian to repair the damage caused by a devastating fire in the reign of Carinus (283). Photo: Shmuel Magal, Sites and Photos.

Diocletian coin, ca. 290-293. Smith College Museum of Art, Nr. SC 1950:4.

Diocletian’s Palace, Fourth Century, Split, Croatia. Peristyle, East Colonnade, arch detail and subterranean rooms and vaults of south section of palace. Photos: Mark Weber/World Monuments Fund and Allan Langdale/Digital Archive of World Architecture.

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