Who divided the Roman Empire into two sections to make it easier to control?

Answer 1

It is sometimes said that the emperor Diocletian split the Roman Empire into an eastern and a western half. This is wrong. The empire was never split. The terms Eastern Western Empire and Western Roman Empire have been coined by historians. The Romans did not use them. They only had one term: Roman Empire. Diocletian created four main administrative subdivisions (not two) when he created what historians have called the tetrarchy (rule by four). These were the four praetorian prefectures.

Diocletian 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. The Caesars were Constantius and Galerius. One of the tasks of the Caesars was to defend the troubled frontiers along the rivers Rhine and Danube respectively. Two of these men were in the west and two were in the east. Diocletian also designated four cites as imperial capitals: Nicomedia (north-western Turkey) was the capital of the praetorian prefectures of Oriens ( the territories in Asia and Egypt) Milan (in northern Italy) was the capital of the praetorian prefecture of Italia et Africa (Italy and north-western Africa), Augusta Trevorum (in south-western Germany) was the capital of the praetorian prefecture of Galliae (Gaul, Britannia and Hispania and Sirmium (in Serbia) was the capital of the praetorian prefecture of Illyricum (most of south-eastern Europe).

Answer 2

Diocletian.