In 312, Constantine defeated Maxentius at the Battle of Milvian Bridge to assume power in Rome. He spent the next few years eliminating his rivals for the throne. By 313, Licinius represented the greatest threat to Constantine. The pair met to establish peace and secure an alliance. Over the next decade, the rivals sporadically waged war upon one another. Constantine finally defeated his final rival at Chrysopolis in 324 to emerge the sole Roman Emperor.
Constantine and Licinius operated under Diocletian’s tetrarchy. Diocletian established a rule of four emperors to govern the empire. Constantine did not wish to operate under the system, but felt compelled to adhere to divided government. In 313, he met Licinius at Milan to establish peaceful relations. Licinius married Constantine’s sister, Constantia, to secure the partnership. The pair also issued the Edict of Milan legalizing Christianity in the Roman Empire.
Licinius cut the Milan summit short to combat a usurper in the east. He defeated the upstart and then relations with Constantine soured. Constantine suffered an assassination attempt which was tied to one of Licinius’ protegees. As relations worsened, Licinius destroyed Constantine’s statues in the east. Constantine defeated his co-emperor at the Battle of Cibalae in 315. Licinius survived to fight again at Mardia in 317. Afterward, the pair reached another peace agreement.
Licinius seemed to be biding his time to strike. In 320, he revoked the Edict of Milan in his territory hoping to provoke Constantine. At the same time, Constantine marched through Licinius’ territories to combat Goths. Constantine responded to Licinius’ complaints over sovereignty and the renewed persecution with an invasion and propaganda campaign.
Constantine defeated his opponent’s naval forces in 323. Then, he laid the ground work for the final invasion with an aggressive propaganda campaign. It became a religious war between Christian and Pagan. At the same time, Licinius’ use of Goth warriors helped transform the conflict between true Romans and foreigners. Constantine’s forces defeated Licinius at Adrianople, the Hellespont, and Chrysopolis. The trio of victories ended Licinius’ emperorship. Constantine allowed Licinius to live as a private citizen. However, the former emperor conspired with barbarians to overthrow the legitimate emperor. In response, Constantine finally executed Licinius.
Constantine consolidated his rule in 324. He spent a decade combating Licinius for control over the Roman Empire. In the end, the two sides used religions and notions of Roman citizenship to fight the other. Constantine emerged victorious and became a historical giant. Licinius became a historical footnote.