Editing Dux (section)

==Roman Empire==

===Original usage===
Until the 3rd century, ''dux'' was not a formal expression of rank within the Roman military or administrative hierarchy.<ref>[[Fergus Millar]], ''The Roman Near East, 31 B.C.-A.D. 337'' (Harvard University Press, 1993), pg. 191 [https://books.google.com/books?id=IA-YlZqHv90C&pg=PA191 online]<!-- ISSN/ISBN needed --></ref>

In the [[Roman army]], a ''dux'' would be a general in charge of two or more legions. While the title of ''dux'' could refer to a [[Roman Consul|consul]] or [[imperator]], it usually refers to the [[Roman governor]] of the [[Roman province|provinces]]. 

In writing his [[Commentarii de Bello Gallico|commentaries]] on the [[Gallic Wars]], [[Julius Caesar]] uses the term only for [[Celt]]ic generals, with one exception for a Roman commander who held no official rank.<ref>[[Thomas Ernst Josef Wiedemann|Thomas Wiedemann]], “The Fetiales: A Reconsideration,” ''Classical Quarterly'' 36 (1986), p. 483. The Roman called ''dux'' is [[Publius Licinius Crassus (son of triumvir)|Publius Crassus]], who was too young to hold a commission; see [[Publius Licinius Crassus (son of triumvir)#Early military career|discussion of his rank]].</ref>

=== Change in usage ===
By the mid-3rd century AD, it had acquired a more precise connotation defining the commander of an expeditionary force, usually made up of detachments (i.e., ''[[Vexillatio|vexillationes]]'') from one or more of the regular military formations. Such appointments were made to deal with specific military situations when the threat to be countered seemed beyond the capabilities of the province-based military command structure that had characterised the Roman army of the High Empire.<ref>{{cite news |last=Smith |first=R. E. |title=Dux; Praepositus |journal=Zeitschrift für Papyrologie und Epigraphik |volume=36 |year=1979 |pages=277–78 }}<!-- ISSN/ISBN needed --></ref>

From the time of [[Gallienus]] onwards for more than a century they were invariably ''Viri Perfectissimi'', i.e., members of the second class of the [[Equites|equestrian order]].<ref>{{cite journal|last=Christol |first=M. |title=Un duc dans une inscription de Termessos (Pisidie) |journal=Chiron |volume=8 |pages=537–38 |year=1978 }}</ref> Thus, they would have out-ranked the commanders of provincial legions, who were usually ''Viri Egregii'' – equestrians of the third class.<ref name="Nagy">{{cite journal|last=Nagy|first=T.|title=Commanders of Legions in the age of Gallienus|journal=Acta Archeologica Hungarica|year=1965|volume=XVII|pages=290–307 }}</ref>

''Duces'' differed from ''[[praeses|praesides]]'' who were the supreme civil as well as military authority within their provinces in that the function of the former was purely military. However, the military authority of a ''dux'' was not necessarily confined to a single province and they do not seem to have been subject to the authority of the governor of the province in which they happened to be operating. It was not until the end of the 3rd century that the term ''dux'' emerged as a regular military rank held by a senior officer of ''[[limitanei]]'' – i.e. frontier troops as opposed those attached to an Imperial field-army (''[[comitatenses]]'') – with a defined geographic area of responsibility.{{NoteTag|The earliest attested ''dux'' with a defined regional responsibility seems to have been Aur. Firminianus, ''dux limit. prov. Scyt ...''<ref>J. B. Campbell, [https://books.google.com/books?id=oCOG74nK81IC&dq=CIL+III+764+%3D+ILS+4103&pg=PA239 CIL III 764 = ILS 4103], "Inscriptions to the Magna Mater in the Provinces of Moesia", ''The Roman Army, 31 BC – AD 337: A Sourcebook'', via [[Google Books]]; accessed 15 May 2016.</ref> – i.e. ''dux'' of the frontier troops of the province of ''Scythia'' – in the 290s AD.}}

===Diocletian's reforms===

Under Diocletion, during the [[Tetrarchy]], a new office called ''dux'' was created with powers split from the role of the governor of a province. The dux was the highest military office within the province and commanded the legions, but the governor had to authorise the use of his powers after which the ''dux'' could act independently and handle all military matters.{{cn|date=June 2024}} The ''[[Dux Belgicae secundae]]'' ("commander of the second Belgic province") is an example.

Also the provinces were reorganised into [[Roman diocese|dioceses]] with each diocese administered by a [[vicarius]]. As with the governors, the vicarius was assisted by a ''dux''. This ''dux'' was superior to all other ''duces'' within the dioceses; when the vicarius called the legions of the dioceses into action, all of the legions were at the command of the ''dux''.{{cn|date=June 2024}} The office of ''dux'' was, in turn, made subject to the [[magister militum]] of his respective [[praetorian prefecture]], and above him to the [[Roman Emperor|emperor]]. The ''Dux per Gallias'' of the diocese of [[Gaul]] is an example of this office.