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Diocletian

Imperator Caesar Gaius Aurelius Valerius Diocletianus Augustus

Reign 284 AD – 305 AD
Dynasty Tetrarchy
Born c. 244 AD
Died c. 311 AD

Diocletian ended the Crisis of the Third Century by establishing the Tetrarchy, a system of four co-emperors dividing responsibility for the vast empire. His sweeping reforms encompassed the military, administration, taxation, and currency. He is the only Roman emperor to voluntarily abdicate, retiring to his palace at Split.

Diocletian transformed the Roman Empire from a barely surviving military autocracy into a reorganized, bureaucratic state. His reforms of administration, taxation, and currency provided the structural foundation on which Constantine and his successors built, even as the Tetrarchic system itself collapsed within years of his abdication.

Key Events

284 AD Accession after the death of Numerian and defeat of Carinus
286 AD Appointed Maximian as co-Augustus, dividing the empire into East and West
293 AD Established the Tetrarchy by appointing Constantius and Galerius as Caesars
296 AD Major currency reform introducing the nummus (follis), argenteus, and reformed aureus
301 AD Edict on Maximum Prices attempting to control inflation; largely unsuccessful
303 AD Launched the Great Persecution, the last and most severe persecution of Christians
305 AD Abdicated voluntarily at Nicomedia; retired to his palace at Split (Spalatum)

Coinage

Diocletian's currency reform of 296 AD was the most comprehensive since Augustus. He introduced the argenteus (a high-purity silver coin), the nummus or follis (a large silvered bronze), and restandardized the aureus. The Tetrarchic coinage features a standardized, non-individualized portrait style emphasizing institutional authority over personality.

Denominations

Aureus Argenteus Nummus (Follis) Radiatus (post-reform antoninianus) Fractional bronze

Notable Types

  • GENIO POPVLI ROMANI types
  • IOVI/HERCVLI types linking the Tetrarchs to Jupiter and Hercules
  • Argenteus with camp-gate or four Tetrarchs sacrificing

Common Reverses

GENIO POPVLI ROMANI PROVIDENTIA DEORVM IOVI CONSERVAT AVGG CONCORDIA MILITVM SACRA MONET AVGG ET CAESS NOSTR VOT XX

Active Mints

Rome Ticinum Aquileia Siscia Serdica Thessalonica Heraclea Nicomedia Cyzicus Antioch Alexandria Carthage London (Londinium) Lyon (Lugdunum) Trier (Augusta Treverorum)

Further Reading

  • Roman Imperial Coinage, Volume VI — C.H.V. Sutherland
  • Coinage in the Roman Economy, 300 B.C. to A.D. 700 — Kenneth W. Harl
← Predecessor Numerian Successor → Maximian