tetrarchies

A tetrarchy, meaning "rule of four," was a system of government where power was divided among four rulers. The most famous example is the Tetrarchy established by the Roman Emperor Diocletian in 293 AD. Diocletian divided the Roman Empire into Eastern and Western halves, appointing two senior emperors, known as Augusti, and two junior emperors, known as Caesars, to rule these respective halves. Each Augustus was responsible for one half of the empire, with a Caesar assisting him and designated to succeed him. The purpose of this system was to provide more efficient administration and defense of the vast Roman Empire. The empire was further subdivided into twelve dioceses, each with its own vicarius, and then into 101 provinces. While initially successful in stabilizing the empire, the Tetrarchy eventually collapsed due to internal power struggles and civil wars among the four rulers. The concept of dividing power among multiple rulers has appeared in other historical contexts, though the Roman Tetrarchy remains the most prominent and studied instance.