<P> Diocletian replaced the prefect of Rome with his consular colleague Bassus . Most officials who had served under Carinus, however, retained their offices under Diocletian . In an act of clementia denoted by the epitomator Aurelius Victor as unusual, Diocletian did not kill or depose Carinus' traitorous praetorian prefect and consul Ti . Claudius Aurelius Aristobulus, but confirmed him in both roles . He later gave him the proconsulate of Africa and the post of urban prefect for 295 . The other figures who retained their offices might have also betrayed Carinus . </P> <P> The assassinations of Aurelian and Probus demonstrated that sole rulership was dangerous to the stability of the empire . Conflict boiled in every province, from Gaul to Syria, Egypt to the lower Danube . It was too much for one person to control, and Diocletian needed a lieutenant . At some time in 285 at Mediolanum (Milan), Diocletian raised his fellow - officer Maximian to the office of caesar, making him co-emperor . </P> <P> The concept of dual rulership was nothing new to the Roman Empire . Augustus, the first Emperor, had nominally shared power with his colleagues, and more formal offices of Co-Emperor had existed from Marcus Aurelius on . Most recently, Emperor Carus and his sons had ruled together, albeit unsuccessfully . Diocletian was in a less comfortable position than most of his predecessors, as he had a daughter, Valeria, but no sons . His co-ruler had to be from outside his family, raising the question of trust . Some historians state that Diocletian adopted Maximian as his filius Augusti, his "Augustan son", upon his appointment to the throne, following the precedent of some previous Emperors . This argument has not been universally accepted . </P> <P> The relationship between Diocletian and Maximian was quickly couched in religious terms . Around 287 Diocletian assumed the title Iovius, and Maximian assumed the title Herculius . The titles were probably meant to convey certain characteristics of their associated leaders . Diocletian, in Jovian style, would take on the dominating roles of planning and commanding; Maximian, in Herculian mode, would act as Jupiter's heroic subordinate . For all their religious connotations, the emperors were not "gods" in the tradition of the Imperial cult--although they may have been hailed as such in Imperial panegyrics . Instead, they were seen as the gods' representatives, effecting their will on earth . The shift from military acclamation to divine sanctification took the power to appoint emperors away from the army . Religious legitimization elevated Diocletian and Maximian above potential rivals in a way military power and dynastic claims could not . </P>

Attempting to restore order to the empire roman emperor diocletian