What happened 324 AD

Then in 324, Constantine, tempted by the "advanced age and unpopular vices" of his colleague, again declared war against him and having defeated his army of 165,000 men at the Battle of Adrianople (3 July 324), succeeded in shutting him up within the walls of Byzantium.

The defeat of the superior fleet of Licinius in the Battle of the Hellespont by Crispus, Constantine's eldest son and Caesar, compelled his withdrawal to Bithynia, where the last stand was made; the Battle of Chrysopolis, near Chalcedon (18 September), resulted in Licinius' final submission.