The Battle of Chrysopolis was fought on 18 September 324 at Chrysopolis (modern Üsküdar), near Chalcedon (modern Kadıköy), between the two Roman emperors Constantine I and Licinius. The battle was the final encounter between the two emperors. After his navy's defeat in the Battle of the Hellespont, Licinius withdrew his forces from the city of Byzantium across the Bosphorus to Chalcedon in Bithynia. Constantine followed, and won the subsequent battle. This left Constantine as the sole emperor, ending the period of the Tetrarchy.