Bureaucratic and military growth, constant campaigning, and construction projects increased the state's expenditures and necessitated a comprehensive tax reform.
From at least 297 on, imperial taxation was standardized, made more equitable, and levied at generally higher rates.
By March 284, Numerian had only reached Emesa (Homs) in Syria; by November, only Asia Minor.
On 20 November 284, the army of the east gathered on a hill 5 kilometres (3.1 mi) outside Nicomedia.
He eventually made his way to northern Italy and made an imperial government, but it is not known whether he visited the city of Rome at this time.
but some modern historians state that Diocletian avoided the city, and that he did so on principle, as the city and its Senate were no longer politically relevant to the affairs of the empire and needed to be taught as much.
It was all good publicity for Diocletian, and it aided in his portrayal of Carinus as a cruel and oppressive tyrant.
Diocletian may have become involved in battles against the Quadi and Marcomanni immediately after the Battle of the Margus.– left his sons Numerian and Carinus as the new Augusti.Carinus quickly made his way to Rome from his post in Gaul as imperial commissioner and arrived there by January 284, becoming legitimate Emperor in the West. The Sassanid king Bahram II could not field an army against them as he was still struggling to establish his authority.Diocletian delegated further on 1 March 293, appointing Galerius and Constantius as Caesars, junior co-emperors.Under this 'tetrarchy', or "rule of four", each emperor would rule over a quarter-division of the empire.The first forty years of his life are mostly obscure.