How did Diocletian seize power after Emperor Carus died?

Following the sudden death of Emperor Carus in 283 and his son Numerian in 284, a succession crisis triggered a Roman civil war. Diocletian, a senior cavalry commander, was proclaimed emperor by the eastern army. He consolidated sole rule of the Roman Empire after defeating Carus's surviving son, Carinus, at the Battle of the Margus in 285.

What we know

• Emperor Carus elevated his eldest son Carinus to co-emperor in 282 before taking his younger son Numerian on campaign against the Sasanian Empire. [2, 3]
• Following the deaths of Carus in 283 and Numerian in 284, the eastern legion proclaimed cavalry officer Diocles (Diocletian) as Roman emperor. [3, 5]
• Diocletian consolidated his power over the Roman Empire by defeating Carinus at the Battle of the Margus in 285. [5]

Still open

• The precise cause of Emperor Carus's death in Mesopotamia and the details surrounding Numerian's subsequent death during the eastern withdrawal remain disputed.

Where to go next

• what followedHow did the Tetrarchy reshape Roman imperial administration?
• what caused itWhy did Emperor Carus invade the Sasanian Empire?
• whereWhere was the Battle of the Margus fought?
• the bigger pictureWhat was the Crisis of the Third Century?
• whoWho was Emperor Carinus?
• an unexpected connectionHow did a retired emperor end up growing cabbages in Croatia?After voluntarily abdicating power in 305, Diocletian retired to his Dalmatian coast palace—which became the core of modern Split—where he spent his final years farming vegetables.

Sources

• [1]Carus (Wikidata Q187004) · CC0 1.0
• [2]Carus · CC BY-SA 4.0
• [3]Carus' Sasanian campaign · CC BY-SA 4.0
• [4]Centres of governance in the Roman Empire · CC BY-SA 4.0
• [5]Diocletian · CC BY-SA 4.0

Your path

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8. /How did Diocletian seize power after Emperor Carus died?