Diocletian brought an end to the period popularly known to historians as the "Crisis of the Third Century" (235–284). He established an autocratic government and was responsible for laying the groundwork for the second phase of the Roman Empire, which is known variously as the "Dominate" (as opposed to the Principate instituted by Augustus), the "Tetrarchy", or simply the "Later Roman Empire". Diocletian 's reforms fundamentally changed the structure of imperial government and helped stabilize the empire economically and militarily, enabling it to remain essentially intact for another hundred years. splitting the Empire into two in order to be more manageable, creating a new system of Imperial succession, ruling as an autocrat and stripping away any remaining façade of republicanism, and economic reforms aimed at the problem of hyperinflation.
These arrangements, while awkward at times and followed more closely by some emperors than others, worked for the first two centuries of the empire 's existence. However, starting with the reign of Septimius Severus, rulers began to strip away or simply ignore many of the republican conventions, and reigned more as dictators than constitutional monarchs. This process undermined the office 's foundations and legitimacy. Diocletian recognized that the title had to be based on something more than simply military force, in order to be more recognized and stable. So he sought to build a new basis for imperial legitimacy in the state religion, with himself as semi-divine monarch and high priest.
Diocletian chose a new title for himself, calling himself Dominus et deus, or "Lord