The third century had been a disaster for the empire. Barbarians had invaded and plundered Roman territory. It seemed as if the empire was about to fall.

Diocletian, with great energy, averted the dissolution of the empire. He used the fighting spirit of the Barbarians by integrating some of them into the Roman army. From his time onward the highest commands were open to Germanic chiefs.

Diocletian reorganized the provinces of the empire, reformed the currency and emphasised the religious nature of his rule. The empire became an absolute monarchy and all citizens were at the disposal of the ruler. The last years of his rule were marked by the last major persecution of Christians.

In 305, wearied by his twenty years in office, Diocletian abdicated. Two new Caesars were selected, Maximinus (305-313) in the east and Severus (305- 307) in the west. Diocletian then retired to his palace at Split on the Croatian coast.