90 Tetrarchy

http://ancienthistory.about.com/od/romeempire/g/tetrarchy.htm

The Tetrarchy in Roman history refers to the division of the Roman Empire into a western and eastern empire, with subordinate divisions within the western and eastern empires.

Tetrarchy comes from the Greek words for four (tetra-) and rule (arch-) or what could be called a quadrumvirate (4-man [rule]) if basing it on Latin, as would seem more apporopriate for a Roman system of rule.

Tetrarchy refers to the establishment by the Roman Emperor Diocletian, in 293, of a 4-part division of the empire. Diocletian continued to rule in the east. He made Maximian his equal and co-emperor in the west. They were each called Augustus which signified that they were emperors. Subordinate to them were the two Caesars: Galerius, in the east, and Constantius in the west. An Augustus was always emperor. Sometimes the Caesars were also referred to as emperors.

This method of creating emperors and their successors bypassed the need for approval of emperors by the Senate and blocked the power of the military to elevate their popular generals to the purple.


The Roman Empire was for a time after 293 ruled by a tetrarchy (a group of four rulers), instituted by Emperor Diocletian. The tetrarchy consisted of two Augusti (senior emperors) and two Caesars (younger emperors). The empire was territorially divided into western and eastern halves, with a senior and a junior emperor in each half. After Diocletian and his colleague, Maximian, retired in 305, internal strife erupted among the tetrarchs. The system finally ceased to exist around 313.