The title was also claimed by Carus' other surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.
Diocletian's reign stabilized the empire and marks the end of the Crisis of the Third Century.
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, Antioch, and Trier, closer to the empire's frontiers than the traditional capital at Rome had been.
In spite of these failures and challenges, Diocletian's reforms fundamentally changed the structure of Roman imperial government and helped stabilize the empire economically and militarily, enabling the empire to remain essentially intact for another 150 years despite being near the brink of collapse in Diocletian's youth.