Diocletian Splits the Throne Four Ways, Then Walks Away From It
What happened
Diocletian took power in November 284 CE after defeating his rival Carinus in battle. Concluding that no single emperor could defend and administer the whole empire against simultaneous threats on multiple frontiers, he split imperial authority between four rulers in a system now called the Tetrarchy: two senior emperors called Augusti, himself in the east and Maximian in the west, and, from 293 CE, two junior emperors called Caesars serving under them, each responsible for a quarter of the empire's defense and government. Diocletian also overhauled the tax base with a new empire-wide census of population and land, issued an Edict on Maximum Prices attempting to curb inflation, and doubled the number of provinces from around fifty to about one hundred. In 305 CE, after a serious illness, he did something almost no Roman emperor had done before: he voluntarily retired, forcing his co-Augustus Maximian to retire alongside him, and withdrew to a purpose-built palace at Split on the Dalmatian coast.
Why it matters
Voluntary retirement from the Roman throne was almost unheard of. Emperors up to this point died in office, were murdered, or were overthrown, but essentially none simply walked away while still capable of ruling. Diocletian's retirement is what exposes the real weakness of the Tetrarchy: the system depended entirely on his personal authority to hold four ambitious men in a cooperative arrangement, and within a few years of his departure the Tetrarchy collapsed into renewed civil war among rival claimants, a conflict Constantine eventually won.
How we know
Diocletian's reforms are documented in the Edict on Maximum Prices itself, a lengthy inscription of price and wage ceilings, fragments of which survive on stone in multiple provinces. His retirement and later life at Split are described by contemporary and near-contemporary writers, and the palace he built survives today as the historic core of the modern city of Split, Croatia.
Sources
- World History Encyclopedia. Diocletian · Reputable sourceworldhistory.org · The domain "worldhistory.org" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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Part of a timelineAncient Rome30 events · From a legendary fratricide on the Palatine Hill to a teenage emperor's quiet deposition twelve centuries later, told through the battles, plagues, and one bridge-crossing that ended a republic.View all →