Editing Tetrarchy (section)

{{short description|Roman system of power division among four rulers}}
{{About|the tetrarchy created by Diocletian|the tetrarchy formed from the kingdom of Herod|Herodian tetrarchy|other uses|Tetrarch (disambiguation)}}
{{more footnotes needed|date=May 2012}}
{{infobox
| abovestyle = font-size:120%; color:#ffffff; background:#b80049;text-align:center;
| above = Roman imperial dynasties
| subheader = [[Tetrarchy|The Tetrarchy]]
| image = [[File:Venice – The Tetrarchs 03.jpg|200px]]
| caption = ''[[Portrait of the Four Tetrarchs]]'', two [[Porphyry (geology)|porphyry]] sculptures looted from the [[Philadelphion]] of Constantinople after 1204, now standing at the southwest corner of [[St Mark's Basilica]], [[Venice]]
| headerstyle = background:#E5E4E2; font-size: 110%;
| header1 = Chronology
| data2 = {{aligned table|fullwidth=y|leftright=y|cols=2
 | '''[[Diocletian]]''' as Augustus
 | {{nowrap|284–286}}
 | — with [[Maximian]] as Caesar
 | 285–286
 | '''[[Maximian]]''' & '''[[Diocletian]]'''<br/> as Augusti of the West and East
 | 286–305
 | — with&nbsp;[[Constantius&nbsp;I]]&nbsp;&&nbsp;[[Galerius]]<br/>as Caesares
 | 293–305
 | '''[[Constantius I]]''' & '''[[Galerius]]'''<br/>as Augusti of West and East
 | 305–306
 | — with [[Severus II]] & [[Maximinus&nbsp;II]]<br/>as Caesares
 |
 | '''[[Severus II]]''' and '''[[Galerius]]''' as Augusti of West and East
 | 306–307
 | — with [[Maximinus II]] and [[Constantine&nbsp;I]] as Caesares
 | 
 | '''[[Maxentius]]''' & '''[[Maximian]]''' as usurpers in Italy and Africa
 | 306–308
 | '''[[Galerius]]''' as Augustus
 | 307–308
 | — with [[Maximinus II]] as Caesar
 | 
 | — with [[Constantine I]] as<br/>self-proclaimed Augustus
 | 
 | '''[[Licinius]]''' & '''[[Galerius]]'''<br/>as Augusti of West and East
 | 308–311
 | — with [[Maximinus II]] and [[Constantine I]] as Caesares
 | 
 | '''[[Maxentius]]''' as usurper in Rome (and Asia Minor 311–312)
 | 308–312
 | '''[[Licinius I]]''' & '''[[Maximinus II]]'''<br/>as Augusti of West and East
 | 311–313
 | — with [[Constantine I]] as<br/>self-proclaimed Augustus
 | 
 | '''[[Constantine I]]''' & '''[[Licinius I]]'''<br/>as Augusti of West and East
 | 313–324
 | — with [[Licinius II]], [[Constantine II (emperor)|Constantine II]] & [[Crispus]] as Caesares
 | 
 | — with '''[[Valerius Valens]]''' as<br/>Augustus of the West
 | 316–317
 | — with '''[[Martinian (emperor)|Martinian]]''' as<br/>Augustus of the West
 | 324
 }}
| header3 = Succession
| data4 = {{aligned table|leftright=y|fullwidth=y
 |''Preceded by''<br/>[[Crisis of the Third Century]]
 |''Followed by''<br/>[[Constantinian dynasty]]
 }}
}}
{{Roman government}}

The '''Tetrarchy''' was the system instituted by [[Roman emperor]] [[Diocletian]] in 293 AD to govern the ancient Roman Empire by dividing it between two emperors, the ''[[augusti]]'', and their junior colleagues and designated successors, the ''[[caesares]]''. 

Initially Diocletian chose [[Maximian]] as his ''caesar'' in 285, raising him to co-''augustus'' the following year; Maximian was to govern the western provinces and Diocletian would administer the eastern ones. The role of the ''augustus'' was likened to [[Jupiter (mythology)|Jupiter]], while his ''caesar'' was akin to Jupiter's son [[Hercules]]. [[Galerius]] and [[Constantius Chlorus|Constantius]] were appointed ''caesares'' in March 293. Diocletian and Maximian retired on 1 May 305, raising Galerius and Constantius to the rank of ''augustus''. Their places as ''caesares'' were in turn taken by [[Valerius Severus]] and [[Maximinus Daza]].

The orderly system of two senior and two junior rulers endured until Constantius died in July 306, and his son [[Constantine the Great|Constantine]] was unilaterally acclaimed ''augustus'' and ''caesar'' by his father's army. Maximian's son [[Maxentius]] contested Severus' title, styled himself ''princeps invictus'', and was appointed ''caesar'' by his retired father in 306. Severus surrendered to Maximian and Maxentius in 307. Maxentius and Constantine were both recognized as ''augusti'' by Maximian that same year. Galerius appointed [[Licinius]] ''augustus'' for the west in 308 and elevated Maximinus Daza to ''augustus'' in 310.

Constantine's victory over Maxentius at the [[Battle of the Milvian Bridge]] in 312 left him in control of the western part of the empire, while Licinius was left in control of the east on the death of Maximinus Daza. Constantine and Licinius jointly recognized their sons – [[Crispus]], [[Constantine II (emperor)|Constantine II]], and [[Licinius II]] – as ''caesares'' in March 317. Ultimately the tetrarchic system lasted until c.&nbsp;324, when mutually destructive civil wars eliminated most of the claimants to power: [[Licinius]] resigned as ''augustus'' after losing the [[Battle of Chrysopolis]], leaving Constantine in control of the entire empire.

The [[Constantinian dynasty]]'s emperors retained some aspects of collegiate rule; Constantine appointed his son [[Constantius II]] as another ''caesar'' in 324, followed by [[Constans]] in 333 and his nephew [[Dalmatius]] in 335, and the three surviving sons of Constantine in 337 were declared joint ''augusti'' together, while the concept of the division of the empire under multiple joint emperors endured until the [[Fall of the Western Roman Empire]]. In the [[Eastern Roman Empire]], ''augusti'' and ''caesares'' continued to be appointed sporadically.