As his replacement he named Martinian co-emperor, as he had previously appointed Valens[7] during his earlier war with Constantine.

Prior to his elevation, which took place some time after the battle of Adrianople, Martinian was serving as magister officiorum at Licinius' court.

[9] In the wake of his defeat at Adrianople Licinius sent Martinian, with an army including Visigothic auxiliaries,[10] to Lampsacus (on the Asiatic shore of the Hellespont or Dardanelles) to prevent Constantine from using his fleet to effect a crossing from Thrace into Mysia and Bithynia in Asia Minor.

[11] Following this defeat, Licinius withdrew his forces from Byzantium, which was being besieged by Constantine, to Chalcedon on the Asiatic shore of the Bosphoros.

Constantine then crossed the Bosphoros to Asia Minor, using a flotilla of light transports he had built independently from his main fleet on the Hellespont, in order to evade the forces of Martinian.