Licinius I

Born around 263 in the Danubian provinces to a modest family, Licinius was a product of the tetrarchic army. He forged his career under Galerius, sharing hard campaigning on the Danube and in Persia, and earned a reputation for endurance, frugality, and loyalty to comrades. At the conference of Carnuntum in 308, Galerius elevated him to Augustus in the West, a sign that the military establishment still preferred seasoned field commanders to senatorial nobles. Licinius married Constantia, Constantine’s half-sister, binding dynastic ties to a political rivalry that would dominate the next decade.

In 313, while in Milan with Constantine, Licinius publicized a policy of toleration and restitution for Christians across their spheres, an act that halted the Great Persecution’s legal legacy and returned confiscated properties. Yet partnership soon curdled into war. At Cibalae in 316, near the Vardar and Sava winds, Constantine’s legions beat Licinius in a brutal, close-fought battle. After an uneasy truce, the struggle reignited. In 324, Constantine struck decisively: he smashed Licinius at Adrianople, drove his fleets onto the Bosporus, and finally broke him at Chrysopolis, the sea and sky thick with sails and smoke. Licinius surrendered, was initially spared for Constantia’s sake, and then executed in 325, closing the era of co-emperors.

Licinius was a soldier-emperor of the old Danubian mold: taciturn, pragmatic, and fiercely jealous of sovereignty. He distrusted court bishops and, in the later years, recoiled from Constantine’s expanding alliance with the churches, sometimes rolling back privileges in the East. His caution could shade into rigidity, and he was less adept at symbolic politics—coinage, monumental messaging, and ecclesiastical patronage—that Constantine used to cultivate broad loyalty. Still, he inspired tough devotion among Balkan and Anatolian troops and understood the logistics of campaigning from Thrace to Bithynia.

Though remembered chiefly as the man Constantine defeated, Licinius helped define the settlement that followed by embodying the last credible alternative: a tetrarchic, army-centered East wary of clerical influence. His co-sponsorship of the 313 toleration edict ensured that Christianity’s legal normalization was imperial, not merely Constantinian. His fall allowed Constantine to claim the mantle of unifier, convene Nicaea, and refound the imperial center at Constantinople. In the central question of this timeline—whether divine legitimacy could end civil war—Licinius’s resistance made the answer decisive: only when he was overcome could a single emperor bind faith and power into one enduring order.