The two decades of Diocletian's reign saw the re-establishment of political, military and economic stability after half a century of chaos, at the price of a more absolutist monarchy, a greatly expanded army and bureaucracy and a more oppressive tax regime. Probably in 286 or 287, a new feature of the imperial collegiality emerged. Diocletian and Maximian began respectively to use the adjectival epithets Iovius and Herculius, bringing themselves into some sort of relationship with the cognate deities, Jupiter and Hercules. The years 287-90 had also seen important developments in the eastern half of the empire, to which Diocletian had repaired after the appointment of Maximian and perhaps a campaign against the Sarmatians in the autumn, reaching Nicomedia in Bithynia by 20 January 286. Iovius for Diocletian and Galerius, Herculius for Maximian and Constantius, epithets survived in the naming of new provincial divisions in Egypt some years after the end of the first tetrarchy.

In 293, two soldiers, Constantius Chlorus and Maximianus Galerius, were raised to the purple as Caesars. The diarchy was transformed into a tetrarchy. With the partition into four areas, the western parts to Maximian and Constantius Chlorus, the eastern to Diocletian himself and Galerius, the centres of decision were brought closer to the more critical frontier zones. It was an attempt to resolve a structural problem in a large territorial Byzantine empire. To strengthen the new regime a new legitimation of imperial power was devised: one that exploited a particular religious climate, while at the same time aiming to trace its roots in the Roman tradition. The administrative reforms, which were connected with the reorganizations of the army, of taxation and even of the coinage, were an effective response to danger from without and to the threat of disintegration. The main feature of Aurelian's reform was the division of the existing provinces into smaller territorial entities.