Diocletian separated and enlarged the empire's civil and military services and reorganized the empire's provincial divisions, establishing the largest and most bureaucratic government in the history of the empire.
He established new administrative centres in Nicomedia, Mediolanum, Sirmium, and Trier, closer to the empire's frontiers than the traditional capital at Rome.
From at least 297 on, imperial taxation was standardized, made more equitable, and levied at generally higher rates.
Not all of Diocletian's plans were successful: the Edict on Maximum Prices (301), his attempt to curb inflation via price controls, was counterproductive and quickly ignored.
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.