Why did Diocletian spit the Roman Empire into different sections?

Answer 1

Diocletian subdivided the Empire into four administrative units and created the tetrarchy (rule by four). He appointed fellow general Maximian as co-emperor in 285. Maximian took overall control of the western part of the empire, while Diocletian took overall control of the eastern part. Then these two men became senior emperors (Augusti) with the creation in 293 of two junior emperors (Caesars) who were subordinates of the Augusti. Diolceitan also created the four praetorian prefectures of Galliae (Gaul, Britannia and Hispania), Italia et Africa, Illyricum (the Balkan Peninsula except for Thracia, in the southeast, next to modern Turkey) and Oriens (Thracia, the territories in Asia and Egypt). . Maximian took charge of Italia et Africa and Diocletian took charge of Oriens.. The Caesars Constantius and Galerius took charge of Galliae and Illyricum respectively. One of the tasks of the Caesars was to defend the troubled frontiers along the rivers Rhine and Danube respectively, which had been under constant attack from outside.

This reform had several aims:

1) The bad experience of recent sole emperors suggested to Diocletian that sole emperors were vulnerable and that co-emperorship made power more secure.

2) Diocletian could not create an informal co-emperorship with a son as previous emperors had done because he was hairless; he had a daughter and no sons. Therefore, he needed a trusted co-ruler from outside the family and had to create a formal co-emperorship

3) There was a need to improve imperial control over the empire. There had been conflict between powerful men in every province of the empire and also attempts at usurpation in some one area. Diocletian shared controlling the provinces with three men.

4) There was also a need to improve the efficiency of the defence of the vast frontiers of the empire. He entrusted the defence of the most troubled tracts of the frontiers to the Caesars.