What happened 313 AD

So in March 313, Licinius married Flavia Julia Constantia, half-sister of Constantine I, at Mediolanum (now Milan); they had a son, Licinius the Younger, in 315.

The Edict of Milan was the February AD 313 agreement to treat Christians benevolently within the Roman Empire. Western Roman Emperor Constantine I and Emperor Licinius, who controlled the Balkans, met in Mediolanum (modern-day Milan) and, among other things, agreed to change policies towards Christians following the edict of toleration issued by Emperor Galerius two years earlier in Serdica. The Edict of Milan gave Christianity legal status and a reprieve from persecution but did not make it the state church of the Roman Empire. That occurred in AD 380 with the Edict of Thessalonica.

On 30 April 313, the two armies clashed at the Battle of Tzirallum, and in the ensuing battle, Daza's forces were crushed. Ridding himself of the imperial purple and dressing like a slave, Daza fled to Nicomedia.

The tetrarchy collapsed, however, in 313 and a few years later Constantine I reunited the two administrative divisions of the Empire as sole Augustus.

Given that Constantine had already crushed his rival Maxentius in 312, the two men decided to divide the Roman world between them. As a result of this settlement, the Tetrarchy was replaced by a system of two emperors, called Augusti: Licinius became Augustus of the East, while his brother-in-law, Constantine, became Augustus of the West. After making the pact, Licinius rushed immediately to the East to deal with another threat, an invasion by the Persian Sassanid Empire.

Maximinus' death was variously ascribed "to despair, to poison, and to the divine justice". Based on descriptions of his death given by Eusebius, and Lactantius, as well as the appearance of Graves' ophthalmopathy in a Tetrarchic statue bust from Anthribis in Egypt, sometimes attributed to Maximinus, endocrinologist Peter D. Papapetrou has advanced a theory that Maximinus may have died from severe thyrotoxicosis due to Graves' disease.