Editing Diocletian (section)

===Maximian made Caesar===
[[File:MSR-ra-34-b-2-DM.jpg|thumb|240x240px|Bust of [[Maximian]], Diocletian's co-ruler in the [[Western Roman Empire]]]]
The assassinations of [[Aurelian]] and Probus demonstrated that sole rulership was dangerous to the stability of the empire.{{sfn|Potter|2005|p=280}} 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.{{sfnm|1a1=Barnes|1y=1981|1p=6|2a1=Southern|2y=2001|2p=136}} According to [[Eutropius (historian)|Eutropius]],{{refn|name=AUG|group="Note"}} Diocletian raised his fellow-officer [[Maximian]] to the office of ''[[Caesar (title)|Caesar]]'', making him his heir and effective co-ruler.{{sfnm|1a1=Barnes|1y=1981|1p=6|2a1=Barnes|2y=1982|2p=4|3a1=CAH|3p=69}}{{sfnm|1a1=Bleckmann|1y=2006|2a1=Corcoran|2y=2006|2p=40|3a1=Potter|3y=2005|3pp=280–281|4a1=Williams|4y=1985|4p=43–45}}

The concept of dual rulership was not new to the Roman Empire. [[Augustus]], the first emperor, had nominally shared power with his colleagues, and a formal office of co-emperor (co-''Augustus'') had existed from [[Marcus Aurelius]] onward.{{sfnm|1a1=Corcoran|1y=2006|1p=40|2a1=Williams|2y=1985|pp=48–49}} Most recently, Carus and his sons had ruled together, albeit unsuccessfully. Dividing the empire in [[Greek East and Latin West|two halves]] was not new either. An informal division was first tested by Marcus Aurelius and his brother [[Lucius Verus]], who spent most of his reign [[Roman–Parthian War of 161–166|campaigning in Persia]], although he returned West shortly before his death. A more formal division occurred in the joint rule of [[Valerian (emperor)|Valerian]]/[[Gallienus]] and [[Carus]]/[[Carinus]]. Diocletian would go on to establish new imperial capitals in both West and East; both halves would become independing of each other in the following decades, with only brief moments of unity.{{sfn|Digeser|2000|pp=25–26}} [[Theodosius I]], the last sole emperor, only ruled alone for a few months before his death in 395 and the permanent split of the empire.

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.{{sfnm|1a1=Potter|1y=2005|1p=280|2a1=Southern|2y=2001|2p=135|3a1=Williams|3y=1985|3p=38}} 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.{{sfnm|1a1=Odahl|1y=2004|1pp=42–43|2a1=Williams|2y=1985|2p=45}} This argument has not been universally accepted.{{sfnm|1a1=CAH|1p=69|2a1=Southern|2y=2001|2p=136}} Diocletian and Maximian added each other's ''[[Roman naming conventions#Nomen|nomina]]'' (their [[family name]], "Valerius" and "Aurelius", respectively) to their own, thus creating an artificial family link and becoming part of the "Aurelius Valerius" family.<ref name="names" />

The relationship between Diocletian and Maximian was quickly couched in religious terms. Around 287 Diocletian assumed the title ''Iovius'' (Jovius), and Maximian assumed the title ''Herculius'' (Hercules).{{sfnm|1a1=CAH|1pp=70–71|2a1=Corcoran|2y=2006|2p=40|3a1=Liebeschuetz|3y=1979|3pp=235–252|4a1=Odahl|4y=2004|4pp=43–44|5a1=Williams|5y=1985|5pp=58–59}} The titles were probably meant to convey certain characteristics of their associated leaders. Diocletian, in [[Jupiter (mythology)|Jovian]] style, would take on the dominating roles of planning and commanding; Maximian, in [[Hercules|Herculian]] mode, would act as Jupiter's [[hero]]ic subordinate.{{sfnm|1a1=Barnes|1y=1981|1pp=11–12|2a1=CAH|2pp=70–71|3a1=Corcoran|3y=2006|3p=40|4a1=Odahl|4y=2004|4p=43|5a1=Southern|5y=2001|5pp=136–137|6a1=Williams|6y=1985|6p=58}} For all their religious connotations, the emperors were not "gods" in the tradition of the [[Imperial cult (ancient Rome)|Imperial cult]]&nbsp;– although they may have been hailed as such in Imperial [[panegyric]]s. Instead, they were seen as the gods' representatives, effecting their will on earth.{{sfnm|1a1=Barnes|1y=1981|1p=11|2a1=CAH|2p=172}} 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.{{sfnm|1a1=Williams|1y=1985|pp=58–59|2a1=CAH|2p=171}}