Dominate

The Dominate was the "despotic" latter phase of government in the ancient Roman Empire from the conclusion of the Third Century Crisis of 235–284 until the formal date of the collapse of the Western Empire in AD 476. It followed the period known as the Principate. In the Eastern half of the Empire, and especially from the time of Justinian I, the system of the Dominate evolved into autocratic absolutism.

The term is derived from the Latin dominus, meaning lord or master, an owner versus his slave—this had been used sycophantically to address emperors from the Julio-Claudian (first) dynasty on, but not used by them as a style—Tiberius in particular is said to have reviled it openly. It became common under Diocletian, who is therefore a logical choice as the first ruler of the "early" dominate. Historian David Potter describes the transformation of government under Diocletian when describing the shifts in imagery the Emperor used to display his power (in this case the building of a huge new palace at Sirmium):

The style of Government so memorably described by Marcus, whereby the emperor sought to show himself as a model of correct aristocratic deportment, had given way to a style in which the emperor was seen to be distinct from all other mortals. His house could no longer be a grander version of houses that other people might live in: it, like him, had to be different.