ON THIS DAY ·
Battle of the Milvian Bridge
28 Oct 312 — Marching under a Christian sign, Constantine defeats Maxentius at the Milvian Bridge over the Tiber. Within a year Christianity is legal; within a century it is the state religion.
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The moment in context
The third-century crisis had exposed two connected problems. Armies needed emperors close enough to respond to danger, yet every army that raised its own candidate threatened to start another civil war. Diocletian’s Tetrarchy gave the empire four legitimate rulers stationed near frontiers: two senior emperors and two junior colleagues intended to succeed them. Government itself acquired a more imposing appearance. From Nicomedia in the Greek east, Diocletian presented the emperor as a sacred, half-divine figure, surrounded by ceremony. Augustus had posed as the first citizen; the new monarchy, often called the Dominate from the Latin for “lord and master,” made the ruler’s exalted position unmistakable.
From Diocletian and Constantine, chapter 9 of The Rise and Fall of Rome, 264 BC – AD 476 (AD 312).
The place: Battle of the Milvian Bridge — map and full story →
Teach this in 5 minutes
- Why it happened — Answers to the third century. The repeated usurpations and failures of the third century shaped Diocletian’s choices. Four rulers addressed the struggle for a single throne;…
- The turn — The Milvian Bridge, 28 October 312. On 28 October 312 Constantine won at the Milvian Bridge under a sign he later linked to Christianity. The sources differ about what he experienced,…
- What it changed — The cost of government. A larger government had to be paid for. Courts, officials and soldiers depended on taxes and compulsory obligations, including those placed on…
Then ask the room: Did the larger state created under Diocletian and Constantine weaken the empire it helped preserve? The argued answer is on the chapter page →
The atlas that shows it
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