Constantine I

On September 18, 324, at the battle of Chrysopolis, Emperor Constantine defeated Emperor Licinius. An excerpt from the article:

"Galerius was serving as the eastern emperor, with and Maximinus Daia as caesar. After Galerius died from cancer (on his deathbed he rescinded all anti-Christian edicts), Maximinus and Licinius fought for control of the east, eventually splitting that part of the empire between them - Licinius got the Balkans while Maximinus got Asia Minor and the eastern provinces. This arrangement was not to last and in 313 CE the two fought on the plains of Thrace. Like Constantine at Milvian Bridge, Licinius fought under the sign of the cross; however, he did it not because of his faith but only to gain the support of the Christians; his opponent, Maximinus, had promised to eradicate them. Despite inferior numbers, Licinius was victorious, and after the suicide of Maximinus, seized control of the east. To be safe and secure in his right to the throne, he immediately executed the sons of both Galerius and Severus, the family of Maximinus, and even Diocletian's daughter.

An uneasy truce existed between Licinius and Constantine, partially because Licinius had married Constantine's half-sister Constantia. In their first meeting on the battlefield In October of 316 CE Constantine defeated him at Cibalae. A second battle near Hadrianopolis ended with land cessions in the Balkans to Constantine. Over the next few years, Licinius's attitude towards the Christians changed with both executions and the destruction of several Christian churches. This was enough to prompt Constantine to gather an army and defeat Licinius in a second battle at Hadrianopolis. The defeated commander fled the battlefield, escaping against the Bosporus. In September of 324 CE Licinius was finally defeated at Chrysopolis and surrendered. Licinius hoped to return to life as a private citizen which Constantine initially granted, but he went back on his word, and Licinius was hanged in 325 CE - even his nine-year-old son was killed. Constantine's victory would reunite the empire."