Diocletian establishes the Tetrarchy

Date

293 CE (system begun 284–286)

Category

Politics & governance

Region

Roman Empire (East and West)

Era

Classical Antiquity

Significance

Proclaimed emperor in 284 CE, Diocletian ended the half-century Crisis of the Third Century through a sweeping reorganisation of imperial power.

In 286 he raised Maximian to co-emperor (Augustus) to govern the west while he ruled the east, and in 293 he formalised the 'rule of four' (Tetrarchy) by appointing two junior emperors (Caesars), Galerius and Constantius Chlorus, each attached to an Augustus with a designated succession. The four rulers governed distinct regions from forward capitals such as Nicomedia, Sirmium, Milan and Trier, bringing imperial authority closer to the threatened frontiers. Alongside the Tetrarchy, Diocletian doubled the number of provinces, separated civil from military commands, expanded the army and bureaucracy, and attempted to halt runaway inflation with the Edict on Maximum Prices in 301. He also launched the empire's last and most severe persecution of Christians from 303. The Tetrarchy restored stability for a generation, but its collusive succession scheme collapsed into civil war after Diocletian's abdication in 305, opening the way for Constantine's rise.

Empires active in 293 CE (system begun 284–286)

• Kingdom of Funan
  50 CE – 550 CE
• Roman Empire
  27 BCE – 476 CE
• Sassanid Empire
  224 CE – 651 CE
• Teotihuacan
  100 BCE – 750 CE
• Kushan Empire
  30 CE – 375 CE
• Zapotec State of Monte Albán
  500 BCE – 800 CE

Related politics & governance events

• Ardashir I defeats the Parthians at Hormozdgan and founds the Sasanian Empire
  28 April 224 CE
• Chandragupta I founds the Gupta Empire and inaugurates the Gupta era
  c. 319–320 CE
• Constantine dedicates Constantinople as a new capital
  11 May 330 CE
• Abdication of Emperor Xian ends the Han; Three Kingdoms begin
  220 CE
• Deposition of Romulus Augustulus ends the Western Roman Empire
  4 September 476 CE
• Augustus founds the Principate (First Settlement)
  16 January 27 BCE

Further reading

SPQR: A History of Ancient Rome

The wider story

SPQR: A History of Ancient Rome

Mary Beard

Bestselling single-volume history of Rome by a leading classicist.

Get it on Amazon →

As an Amazon Associate, Human Saga earns from qualifying purchases.