Europe 324: Battle of Chrysopolis
In 324 Constantine invaded Licinius’ territory in Thracia, scoring victories at Adrianople, Byzantium, and in a naval battle in the Hellespont. Constantine then crossed into Asia, where he decisively defeated Licinius at Chrysopolis, bringing an end to the 18-year-long civil wars of the Tetrarchy and reuniting the Roman Empire.
3 Jul 324 Battle of Adrianople▲
In the early summer of 324 Constantine invaded Thraciae, advancing to the River Hebrus, on the outskirts of Adrianople, where Licinius and his army had gathered. Constantine diverted his opponent’s attention by feigning the construction of a bridge, then forded the river with a small force further upstream. In danger of being outflanked, Licinius withdrew to higher ground, where he was defeated by Constantine in a day-long battle.
Jul–Sep 324 Siege of Byzantium▲
Following his defeat at Adrianople in July 324, Licinius withdrew to Byzantium, which was quickly besieged by Constantine. After the defeat of Licinius’ fleet, Constantine’s navy joined the blockade and he raised a high mound against the city walls, making use of it to deploy numerous siege engines against the city. Alarmed by these measures, Licinius fled across the Bosporus to Chalcedon with a small force of loyalists and in September Byzantium surrendered to Constantine.
Jul 324 Battle of the Hellespont▲
While Constantine was besieging Licinius in Byzantium, a fleet of 80 of his best war galleys under the command of his son Crispus sailed into the Hellespont and attacked a fleet of 200 under the command of Licinius’ admiral Abantus. By the time nightfall forced both fleets into harbor, Crispus seemed to be winning, but the next day Abantus emerged to fight again. However, just as the arrival of new enemy vessels made him hesitate, the wind changed and a devastating southerly destroyed almost all of Abantus’ fleet, leaving him to escape to Asia with just four ships and ending Licinius’ naval hopes.
18 Sep 324 Battle of Chrysopolis▲
Having secured naval supremacy, Constantine crossed the Bosporus in September 324 and established himself near Chrysopolis. Licinius, who had rallied a new army in Asia, marched out to face him but Constantine attacked first and swiftly defeated him. The next day Consantia, Licinius’ wife and Constantine’s sister, persuaded Constantine to spare his rival’s life and Licinius was allowed to live in security in Thessalonica. However, the following year Constantine accused him of conspiring against him, possibly with the Tervingi Goths, and had him executed.