Tetrarchy

The tetrarchy was the system of government involving four rulers instituted by Roman Emperor Diocletian in 293 CE, marking the end of the crisis of the third century, and the recovery of the Roman Empire. This Tetrarchy lasted until c.313 CE, when internal conflict eliminated most of the claimants to power, leaving Constantine in the West and Licinius in the East. The first tetrarchy was composed of Constantius (Constantine's father) and Severus II in the west, and Galerius and Maximinus in the east. Constantine reunited the two halves of the Roman Empire in 324, after defeating Licinius.