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Today in History: Constantine defeats Licinius, ends Roman Tetrarchy

By Drooid · Sep 18, 2026, 10:36 AM UTC · How we work

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Summary

Story summary

On 18 September 324, Constantine I crushed rival emperor Licinius at Chrysopolis, opposite Byzantium on the Bosphorus. After his son Crispus destroyed Licinius’s fleet at the Hellespont, Licinius regrouped at Chalcedon with Visigothic auxiliaries and Martinian’s troops, but Constantine’s forces prevailed, ending the Tetrarchy and securing sole rule of the Roman Empire.

1 of 1

Story summary

On 18 September 324, Constantine I crushed rival emperor Licinius at Chrysopolis, opposite Byzantium on the Bosphorus. After his son Crispus destroyed Licinius’s fleet at the Hellespont, Licinius regrouped at Chalcedon with Visigothic auxiliaries and Martinian’s troops, but Constantine’s forces prevailed, ending the Tetrarchy and securing sole rule of the Roman Empire.