Editing Diocletian (section)

==Early rule==
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Diocletian may have become involved in battles against the [[Quadi]] and [[Marcomanni]] immediately after the Battle of the Margus. He eventually made his way to northern Italy and made an imperial government, but it is not known whether he visited Rome at this time.{{sfnm|1a1=Barnes|1y=1981|1p=5|2a1=CAH|2p=69}} There is a contemporary issue of coins suggestive of an imperial ''[[adventus (ceremony)|adventus]]'' (arrival) for the city,<ref>''[[Roman Imperial Coinage]]'' Vol 5.2.241 no. 203–204</ref>{{sfnm|1a1=Barnes|1y=1981|1p=5|2a1=Barnes|2y=1982|2p=50}} but some modern historians state that Diocletian avoided the city, to demonstrate that the city and its Senate were no longer politically relevant to the affairs of the empire.{{sfn|Williams|1997|p=41}} Diocletian dated his reign from his elevation by the army, not his ratification by the Senate,{{sfn|Williams|1985|p=41}} following the practice established by Carus, who had declared the Senate's ratification a useless formality.{{sfn|Epit. Caesaribus|loc=37.5}} Diocletian offered proof of his deference towards the Senate by retaining Aristobulus as ordinary consul and colleague for 285 (one of the few instances during the Late Empire in which an emperor admitted a ''[[privatus]]'' as his colleague)<ref>{{cite book |last=Barnes |year=1998 |first=Timothy D. |title=Ammianus Marcellinus and the Representation of Historical Reality |location=Ithaca |publisher=Cornell University Press |page=46 |isbn=0-8014-3526-9 |title-link=iarchive:ammianusmarcelli0000barn}}</ref> and by creating senior senators Vettius Aquilinus and Junius Maximus ordinary consuls for the following year&nbsp;– for Maximus, it was his second consulship.{{sfn|PLRE|loc=Vol 1, "[https://archive.org/details/prosopography-later-roman-empire/PLRE-I/page/586 M. Iunius Maximus 38]", p. 587}}

If Diocletian did enter Rome shortly after his accession, he did not stay long;{{sfn|Southern|2001|pp=135, 331}} he is attested back in the Balkans by 2 November 285, on campaign against the [[Sarmatians]].{{sfn|Potter|2005|p=281}}

Diocletian replaced the [[Praefectus urbis|prefect]] of Rome with his consular colleague Bassus. Most officials who had served under Carinus retained their offices under Diocletian.{{sfnm|1a1=Barnes|1y=1981|1pp=5–6|2a1=CAH|2p=69|3a1=Barnes|3y=1982|3p=113|4a1=Williams|4y=1985|4pp=41–42}} In an act of ''clementia'' denoted by the epitomator of [[Aurelius Victor]] as unusual,{{sfn|Epit. Caesaribus|loc=39.15}} Diocletian did not kill or depose Carinus's traitorous praetorian prefect and consul [[Titus Claudius Aurelius Aristobulus|Aristobulus]], but confirmed him in both roles.{{sfnm|1a1=Barnes|1y=1975|1p=46|2a1=Barnes|2y=1981|2pp=5–6|3a1=Leadbetter|3y=2001b|4a1=Williams|4y=1985|4p=41}} He later gave him the proconsulate of Africa and the post of urban prefect for 295.{{sfn|Leadbetter|2001b}} The other figures who retained their offices might have also betrayed Carinus.{{sfnm|1a1=Barnes|1y=1975|1p=46|2a1=Barnes|2y=1981|2pp=5–6|3a1=Leadbetter|3y=2001b}}

===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}}

===Conflict with Sarmatia and Persia===
After his acclamation, Maximian was dispatched to fight the rebel [[Bagaudae]], insurgent peasants of Gaul. Diocletian returned to the East, progressing slowly.{{sfnm|1a1=Barnes|1y=1981|1p=6|2a1=Southern|2y=2001|2p=137}} By 2 November, he had only reached Civitas Iovia (Botivo, near [[Ptuj]], [[Slovenia]]).<ref>''[[Codex Justinianus]]'' 4.48.5; ''[[Fragmenta Vaticana]]'' 297</ref>{{sfnm|1a1=Barnes|1y=1981|1p=6|2a1=Barnes|2y=1982|2p=50|3a1=Potter|3y=2005|3p=281}} In the Balkans during the autumn of 285, he encountered a tribe of [[Sarmatians]] who demanded assistance. The Sarmatians requested that Diocletian either help them recover their lost lands or grant them pasturage rights within the empire. Diocletian refused and fought a battle with them, but was unable to secure a complete victory. The nomadic pressures of the [[European Plain]] remained and could not be solved by a single war; soon the Sarmatians would have to be fought again.{{sfnm|1a1=Southern|1y=2001|1p=143|2a1=Williams|2y=1985|2p=52}}

Diocletian wintered in [[Nicomedia]].{{refn|He is placed there by a rescript dated 3 March 286.<ref>''[[Fragmenta Vaticana]]'' 275</ref>{{sfnm|1a1=Barnes|1y=1981|1p=6|2a1=Potter|2y=2005|2pp=281, 649}}|group="Note"}} There may have been a revolt in the eastern provinces at this time, as he brought settlers from [[Asia (Roman province)|Asia]] to populate emptied farmlands in [[Thrace]].{{sfn|Barnes|1981|p=6; ''[[Panegyrici Latini]]'' 8(5)21.1}} He visited [[Syria Palaestina]] the following spring,{{refn|He is attested there in a rescript dated 31 May 287.{{sfn|Cod. Justinianus|loc=4.10.3; 1.51.1; 5.17.3}}{{sfnm|1a1=Barnes|1y=1981|1p=6|2a1=Barnes|2y=1982|2pp=50–51|3a1=Potter|3y=2005|3pp=281, 649}} The Jewish ''[[Midrash]]'' suggests that Diocletian resided at Panias (present-day Banias) in the northern Golan Heights.<ref>[[Midrash Rabba]] (Genesis), Ed. Vilna, Parashas Toledos 63:8.</ref>|group="Note"}} His stay in the East saw diplomatic success in the conflict with Persia: in 287, [[Bahram II]] granted him precious gifts, declared open friendship with the Empire, and invited Diocletian to visit him.{{sfnm|1a1=Barnes|1y=1981|1p=6|2a1=Millar|2y=1993|2p=177}} Roman sources insist that the act was entirely voluntary.{{sfn|Southern|2001|p=242}}

Around the same time, perhaps in 287,{{sfnm|1a1=Barnes|1y=1982|1p=51|2a1=CAH|2p=73}} Persia relinquished claims on [[Armenia]] and recognized Roman authority over territory to the west and south of the Tigris. The western portion of Armenia was incorporated into the empire and made a province. [[Tiridates III of Armenia|Tiridates III]], the [[Arsacid dynasty of Armenia|Arsacid]] claimant to the Armenian throne and a Roman client, had been disinherited and forced to take refuge in the empire after the Persian conquest of 252–53. In 287, he returned to lay claim to the eastern half of his ancestral domain and encountered no opposition.{{sfnm|1a1=Barnes|1y=1981|1p=6|2a1=CAH|2p=73|3a1=Potter|3y=2005|3pp= 292, 651|4a1=Southern|4y=2001|4p=143|5a1=Williams|5y=1985|5p=52}} Diocletian was hailed as the "founder of eternal peace". The events might have represented a formal end to Carus's eastern campaign, which probably ended without an acknowledged peace.{{sfn|Southern|2001|pp=242, 360–361}} At the conclusion of discussions with the Persians, Diocletian re-organized the Mesopotamian frontier and fortified the city of [[Circesium]] (Buseire, Syria) on the [[Euphrates]].{{sfnm|1a1=CAH|1p=73|2a1=Millar|2y=1993|2pp=180–181|3a1=Southern|3y=2001|3p=143|4a1=Williams|4y=1985|4p=52}}

===Maximian made Augustus===
[[File:5 Aurei, Diocletian and Maximianus Herculius, Elephantenquadriga, Rome, 287 AD - Bode-Museum - DSC02724.JPG|thumb|Diocletian and Maximian on an aureus (AD&nbsp;287)]]
Maximian's campaigns were not proceeding as smoothly. The Bagaudae had been easily suppressed, but [[Carausius]], the man he had put in charge of operations against [[Saxons|Saxon]] and [[Franks|Frankish]] [[Piracy|pirates]] on the [[Saxon Shore]], had, according to literary sources, begun keeping the goods seized from the pirates for himself. Maximian issued a death warrant for his larcenous subordinate. Carausius fled the Continent, proclaimed himself emperor, and agitated Britain and northwestern Gaul into open revolt against Maximian and Diocletian.{{sfnm|1a1=Barnes|1y=1981|1pp=6–7|2a1=CAH|2pp=70–71|3a1=Potter|3y=2005|3pp=283–284|4a1=Southern|4y=2001|4pp=137–141|5a1=Williams|5y=1985|5pp=45–47}}

Far more probable, according to the archaeological evidence, is that Carausius had held some important military post in Britain,{{sfn|Southern|2001|p=138}} already had a firm basis of power in Britain and Northern Gaul, and profited from the lack of legitimacy of the central government.{{sfn|Potter|2005|p=284}} Carausius strove to have his legitimacy as a junior emperor acknowledged by Diocletian: in his coinage, he extolled the "concord" between him and the central power. One bronze piece from 290 read PAX AVGGG, "the Peace of the three Augusti"; on the other side, it showed Carausius together with Diocletian and Maximian, with the caption CARAVSIVS ET FRATRES SVI, "Carausius & his brothers".{{sfn|Southern|2001|pp=138, 140}}<ref>{{cite web|author=Stephen J. Murray|year=2021|url=http://www.dot-domesday.me.uk/empires2.htm|title=New Empires|website=From Dot To Domesday – British History|access-date=20 January 2023|archive-date=14 October 2021|archive-url=https://web.archive.org/web/20211014181832/http://www.dot-domesday.me.uk/empires2.htm|url-status=live}}</ref> Diocletian could not allow a breakaway regional usurper following in [[Postumus]]'s footprints to enter, of his own accord, the imperial college.{{sfn|Williams|1985|pp=61–62}}

Spurred by the crisis, on 1 April 286,{{sfnm|1a1=Barnes|1y=1981|1pp=6–7|2a1=CAH|2p=69|3a1=Potter|3y=2005|3p=282|4a1=Southern|4y=2001|4pp=141–142|5a1=Williams|5y=1985|5pp=47–48}}{{refn|name=AUG|The chronology of Maximian's appointment as co-ruler is somewhat uncertain.{{sfnm|1a1=Corcoran|1y=2006|1p=40|2a1=Southern|2y=2001|2p=142}} Some argue that Maximian was appointed ''Augustus'' without ever holding the office of ''Caesar''.{{sfn|Southern|2001|p=142, "It has also been suggested that Maximian became Augustus at the very beginning of Diocletian’s reign. The chronology is not established  beyond doubt"}} 1 April 286, the date given by the 5th-century ''[https://archive.org/details/chronicaminorasa09momm/page/229/mode/1up Consularia Constantinopolitana]'', is the most common date used in modern histories for Maximian's ''[[dies imperii]]''.{{sfnm|1a1=Barnes|1y=1981|1pp=6–7|2a1=CAH|2p=69|3a1=Potter|3y=2005|3p=282|4a1=Southern|4y=2001|4pp=141–142|5a1=Williams|5y=1985|5pp=47–48}} A document dated 31 March 286 already shows Diocletian and Maximian as joint emperors. The ''CAH'' dates the assumption of the Augustan title to 1 March 286.{{sfn|CAH|p=69; following ''[[Berliner griechische Urkunden|BGU]]'' 4.1090.34}} According to a recent view, Maximian was appointed ''Augustus'' (without ever being ''Caesar'') on or around 13 December 285.{{sfnm|1a1=Burgess|1y=2023|2a1=Nixon|2a2=Rodgers |2y=2023|2pp=44-51}}|group="Note"}} Maximian took up the title of ''Augustus'' (emperor).{{sfnm|1a1=Barnes|1y=1981|1p=7|2a1=Bleckmann|2y=2006|3a1=Corcoran|3y=2006|3p=40|4a1=Potter|4y=2005|4p=282|5a1=Southern|5y=2001|5pp=141–142|6a1=Williams|6y=1985|6p=48}} Unusually, Diocletian could not have been present to witness it. It has even been suggested that Maximian usurped the title and was only later recognized by Diocletian in hopes of avoiding civil war.{{sfn|Potter|2005|p=649}} This suggestion is unpopular, as it is clear that Diocletian meant for Maximian to act with a certain amount of independence.{{sfnm|1a1=Potter|1y=2005|1p=282|2a1=Williams|2y=1985|2p=49}} It may be posited that Diocletian felt the need to bind Maximian closer to him, by making him his empowered associate, to avoid the possibility of him striking some sort of deal with Carausius.{{sfn|Southern|2001|p=141}}
[[File:Rare Carausius Denarius.jpg|left|thumb|[[Carausius]], rebel emperor of [[Roman Britain|Britain]]. Most of the evidence for his reign comes from his coinage, which was of generally fine quality.{{sfn|Southern|2001|p=140}}]]
Maximian realized that he could not immediately suppress the rogue commander, so in 287 he campaigned against tribes beyond the [[Rhine]] instead.{{sfnm|1a1=Barnes|1y=1981|1p=7|2a1=CAH|2p=71|3a1=Corcoran|3y=2006|3p=40}} As Carausius was allied to the Franks, Maximian's campaigns could be seen as an effort to deny him a basis of support on the mainland.{{sfn|Williams|1985|p=62}} The following spring, as Maximian prepared a fleet for an expedition against Carausius, Diocletian returned from the East to meet Maximian. The two emperors agreed on a joint campaign against the [[Alamanni]]. Diocletian invaded Germania through Raetia while Maximian progressed from Mainz. Each burned crops and food supplies as he went, destroying the Germans' means of sustenance.<ref>{{cite book|last=Rees|first=Roger|title=Layers of Loyalty in Latin Panegyric|year=2002|location=Oxford |publisher=Oxford University Press|isbn=978-0-19-924918-3|doi=10.1093/acprof:oso/9780199249183.001.0001}}</ref>{{sfnm|1a1=Southern|1y=2001|1pp=142–143|2a1=Williams|2y=1985|2p=50}} The two men added territory to the empire and allowed Maximian to continue preparations against Carausius without further disturbance.{{sfnm|1a1=Barnes|1y=1981|1p=7|2a1=Corcoran|2y=2006|2p=40|3a1=Southern|3y=2001|3p=143}} On his return to the East, Diocletian managed what was probably another rapid campaign against the resurgent Sarmatians. No details survive, but surviving inscriptions indicate that Diocletian took the title ''Sarmaticus Maximus'' after 289.{{sfnm|1a1=Barnes|1y=1982|1p=255|2a1=Southern|2y=2001|2p=144}}

In the East, Diocletian engaged in diplomacy with desert tribes in the regions between Rome and Persia. He might have been attempting to persuade them to ally themselves with Rome, thus reviving the old, Rome-friendly, [[Palmyra|Palmyrene]] [[sphere of influence]],{{sfn|Potter|2005|p=285}} or to reduce the frequency of their incursions.{{sfn|Williams|1985|p=63}} No details survive for these events.{{sfn|Southern|2001|p=144}} Some of the princes of these states were Persian client kings, a disturbing fact for the Romans in light of increasing tensions with the Sassanids.{{sfn|Williams|1985|p=78}} In the West, Maximian lost the fleet built in 288 and 289, probably in the early spring of 290. The [[panegyric|panegyrist]] who refers to the loss suggests that its cause was a storm,<ref>''[[Panegyrici Latini]]'' 8(5)12.2</ref>{{sfnm|1a1=Barnes|1y=1981|1pp=7, 288|2a1=Potter|2y=2005|2pp= 284–285, 650|3a1=Southern|3y=2001|3p=143|4a1=Williams|4y=1985|4p=55}} but this might have been an attempt to conceal an embarrassing military defeat.{{sfnm|1a1=Southern|1y=2001|1p=143|2a1=Williams|2y=1985|2p=55}} Diocletian broke off his tour of the Eastern provinces soon thereafter. He returned with haste to the West, reaching Emesa by 10 May 290,{{sfn|Cod. Justinianus|loc=9.41.9}}{{sfnm|1a1=Barnes|1y=1982|1p=51|2a1=Potter|2y=2005|2pp=285, 650}} and Sirmium on the Danube by 1 July 290.{{sfn|Cod. Justinianus|loc=6.30.6}}{{sfnm|1a1=Barnes|1y=1982|1p=52|2a1=Potter|2y=2005|2pp=285, 650}}

Diocletian met Maximian in Milan either in late December 290 or January 291.{{sfnm|1a1=Barnes|1y=1981|1p=8|2a1=Barnes|2y=1982|2p=52|3a1=Potter|3y=2005|3p=285}} The meeting was undertaken with a sense of solemn pageantry. The emperors spent most of their time in public appearances. It has been surmised that the ceremonies were arranged to demonstrate Diocletian's continuing support for his faltering colleague.{{sfn|Potter|2005|p=285}} A deputation from the Roman Senate met with the emperors, renewing its infrequent contact with the Imperial office.<ref>''[[Panegyrici Latini]]'' 11(3)2.4, 8.1, 11.3–4, 12.2.</ref>{{sfnm|1a1=Barnes|1y=1981|1pp=8, 288|2a1=Potter|2y=2005|2pp=285, 650|3a1=Williams|3y=1985|3p=56}} The choice of Milan over Rome further snubbed the capital's pride. But then it was already a long-established practice that Rome itself was only a ceremonial capital, as the actual seat of the Imperial administration was determined by the needs of defense. Long before Diocletian, [[Gallienus]] (r. 253–68) had chosen Milan for his headquarters.{{sfn|Elsner|1998|p=73}} If the panegyric detailing the ceremony implied that the true center of the empire was not Rome, but where the emperor sat ("...the capital of the empire appeared to be there, where the two emperors met"),{{sfn|Williams|1985|p=57; quoting the ''[[Panegyrici Latini]]'' 11(3)12}} it simply echoed what had already been stated by the historian [[Herodian]] in the early third century: "Rome is where the emperor is".{{sfn|Elsner|1998|p=73}} During the meeting, decisions on matters of politics and war were probably made in secret.{{sfnm|1a1=Barnes|1y=1981|1p=8|2a1=Potter|2y=2005|2pp=285, 288}} The ''Augusti'' would not meet again until 303.{{sfn|Potter|2005|p=285}}