Diocletian divided his empire into what?

Answer 1

Emperor Diocletian created the tetrarchy (rule by four). He appointed fellow general Maximian as co-emperor who took charge of the western part of the empire, while he took charge of the eastern part. These two men became senior emperors (Augusti) with the creation of two junior emperors (Caesars). The latter two took charge of defending the troubled frontiers along the rivers Rhine and Danube respectively, which were under constant attack from outside.

This created four administrative divisions. Diocletian took charge of the territories in Asia. Maximilian took charge of Italy and Africa. One junior emperor took charge of Britain, Gaul and Spain and the other took charge of the Balkan Peninsula in southeastern Europe. This reform improved the efficiency of the defence of the vast frontier of the empire. It was not a division of the empire which, as Diocletian stressed, was indivisible. It was an administrative arrangement.

Co-emperorship was not new. Previously emperors had made their sons co-emperors with one in charge of the east and the other in charge of the east. The purpose was the same, improving the defence of the frontiers. After the tetrarchy, there was an alternation of periods of co-emperorship and periods with a sole emperor.