Licinius, also known as Valerius Licinianus Licinius, was a Roman emperor who reigned from 308 to 324 CE. Born to a Dacian peasant family, he rose through the ranks of the Roman army and was a close friend and companion of Emperor Galerius.
Early Life and Rise to Power: Little is known about Licinius's early life. He served with distinction under Galerius, accompanying him on his Persian campaign. In 308, during the Conference of Carnuntum, Galerius appointed Licinius as Augustus in the West, with control over the provinces of Illyricum, Thrace, and Pannonia. This appointment was a move to stabilize the tetrarchy after the death of Severus II and the usurpation of Maxentius in Rome.
Co-Reign with Constantine: Licinius initially shared power uneasily with Maximinus Daia in the East and Constantine I in the West. His first major challenge came in 312 when Constantine defeated Maxentius at the Battle of the Milvian Bridge, gaining control of the entire Western Roman Empire. Recognizing the shifting balance of power, Licinius formed an alliance with Constantine. In 313, they met in Mediolanum (modern Milan) and issued the Edict of Milan, which granted religious tolerance throughout the Roman Empire, effectively ending the persecution of Christians. To solidify their alliance, Licinius married Constantia, Constantine's half-sister.
Shortly after the Edict of Milan, Licinius engaged Maximinus Daia in battle. Maximinus, who had invaded Thrace, was decisively defeated by Licinius at the Battle of Tzirallum in April 313. Maximinus fled and died later that year, leaving Licinius as the sole Augustus in the East.
Conflict with Constantine and Downfall: Despite their initial alliance, tensions between Licinius and Constantine began to mount. Both emperors harbored ambitions for sole rule, and their respective territories bordered each other, leading to inevitable friction.
- First Civil War (316/317 CE): The first major conflict erupted in 316 (or possibly late 314). Constantine claimed Licinius was harboring a co-conspirator, Bassianus. The war began with the Battle of Cibalae, where Constantine inflicted a heavy defeat on Licinius. A second engagement, the Battle of Mardia (also known as Campus Ardiensis), was inconclusive. A peace treaty was signed in Serdica (modern Sofia), in which Licinius ceded Illyricum, Pannonia, and Moesia to Constantine. Licinius also had to accept Constantine's two sons, Crispus and Constantine II, as Caesars, alongside his own son, Licinius II.
- Second Civil War (324 CE): The truce lasted for several years, but underlying tensions persisted. Licinius began to reverse the policies of the Edict of Milan within his domain, particularly targeting Christians, perhaps seeing them as Constantine's supporters. This religious persecution, along with ongoing border disputes and mutual suspicions, led to the final confrontation. In 324, Constantine launched a full-scale invasion of Licinius's territory.
- Constantine defeated Licinius at the Battle of Adrianople in July 324.
- Licinius retreated to Byzantium, where he was besieged.
- Licinius's navy was destroyed by Constantine's son Crispus at the Battle of the Hellespont.
- Licinius raised new forces but was decisively defeated for the final time at the Battle of Chrysopolis (near Chalcedon) in September 324.
Death: After the Battle of Chrysopolis, Licinius fled but was eventually persuaded to surrender by his wife Constantia, who pleaded with her brother Constantine for her husband's life. Constantine initially spared Licinius, confining him to Thessalonica. However, in 325 CE, Constantine ordered Licinius's execution, officially on the grounds of conspiring to raise new troops. Licinius's son, Licinius II, was also executed around the same time, possibly in 326 CE. With Licinius's death, Constantine became the sole emperor of the Roman Empire, bringing an end to the Tetrarchy.