Diocletian

Gaius Aurelius Valerius Diocletianus was born around 244 CE near Salona in Dalmatia — modern Split, Croatia — the son of a freedman or scribe; he was one of the most spectacularly self-made men in Roman history. He rose through the ranks of the cavalry, served under the soldier-emperors of the crisis years, and was the commander of Numerian's bodyguard when Numerian was found dead in his closed litter in November 284 CE. The army blamed the praetorian prefect Aper; Diocletian struck him down personally before the assembled troops, proclaiming 'This is the man who murdered Numerian.' He was acclaimed Augustus on the spot. Within a year he had defeated Numerian's brother Carinus at the Battle of the Margus River in 285 CE and ruled the empire alone — but not for long. The Roman Empire in 284 CE was a machine in crisis: barbaric invasions on every frontier, hyperinflation that had destroyed the currency, an army whose loyalty could be bought by the nearest usurper. Diocletian's solution was systematic and unprecedented. In 285 CE he appointed his trusted officer Maximian as Caesar, then elevated him to co-Augustus in 286 CE, dividing the empire into eastern and western commands. In 293 CE he went further, appointing two more officers — Galerius and Constantius Chlorus — as Caesars subordinate to each Augustus. This was the Tetrarchy: four co-rulers sharing power, each controlling a quarter of the empire, each paired with a junior colleague who would inherit. It was the most radical constitutional innovation Rome had seen since Augustus invented the Principate. Diocletian based himself in Nicomedia in Asia Minor (modern İzmit), which he made effectively the eastern , transforming it with new buildings. The system worked. Usurpations slowed dramatically. Frontiers were stabilised. Diocletian personally campaigned in Egypt in 296–298 CE, suppressing a revolt and reorganising the province; in 297–298 CE, Galerius invaded Persia and won stunning victories, seizing five provinces beyond the Tigris in the Peace of Nisibis (298 CE) — the most favourable treaty Rome had extracted from Persia in over three centuries. Diocletian's administrative reforms were equally transformative. He nearly tripled the number of provinces, reducing their size to make them more governable; military and civilian commands, previously combined, were separated. He reformed the coinage, introducing the gold aureus on a new standard. His Edict on Maximum Prices (301 CE) — the longest surviving Roman document, inscribed across dozens of stone tablets across the empire — attempted to fix prices for hundreds of goods and wage rates for every conceivable occupation, from barristers to camel-drivers. It failed within months but remains an unparalleled window into the economy of the ancient world. The darkest act of his reign began in February 303 CE. Galerius persuaded Diocletian that the Christians — perhaps five to ten percent of the empire's population by this point — were a threat to the traditional Roman religious order. The Great Persecution that followed was the most sustained and systematic attack on Christianity in Roman history: churches destroyed, scriptures confiscated, clergy imprisoned, sacrifices demanded on pain of death. Tens of thousands were killed or tortured across the eastern empire over the next decade, though the persecution was inconsistently applied in the west. It failed. On 1 May 305 CE, Diocletian did something no Roman emperor before him had voluntarily done: he abdicated. In a formal ceremony at Nicomedia, wearing his imperial purple, he laid it down. He compelled his co-Augustus Maximian to abdicate simultaneously. He retired to his palace at Salona — the city-sized fortress he had been building for years on the Dalmatian coast — and grew vegetables. When the Tetrarchic system collapsed immediately after his departure, and rivals begged him to return, he reportedly replied: 'If you could see the cabbages I have planted at Salona with my own hands, you would not urge such a step on me.' He died in 311 CE, probably of natural causes, in his palace. His mausoleum is now the cathedral of Split. Diocletian's Palace itself survives at the core of the modern city — 30,000 square metres of late Roman imperial architecture, still inhabited.

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