Siege of Byzantium
324 CE.
Shown on the map at 41.015°, 28.985°.
The siege of Byzantium was carried out some time between July and September 324 by the forces of the Roman emperor Constantine I (r. 306–337) during his Second Civil War against his rival, co-emperor Licinius (r. 308–324). It would have been started simultaneously with the naval battle of the Hellespont (today known as Dardanelles) in which Constantine's son and caesar Crispus (r. 317–326) defeated the Lycinian navy commanded by Admiral Abanto. The victory on the Hellespont made it possible to prolong the siege of Byzantium and forced Licinius to summon the forces that were quartered in the city to Asia Minor, where the emperor intended to regroup his remaining forces to confront Constantine again. However, he would be defeated at the consecutive battle of Chrysopolis, ending the Tetrarchy system and allowing the Constantine to establish himself as sole ruler of the Roman Empire. This was the tenth significant siege of the city, and there were to be many more.
Text from the Wikipedia article Siege of Byzantium (324), licensed CC BY-SA 4.0.