Editing Roman legion (section)

=== Later Empire (from 284 AD) ===
{{Main|Late Roman army}}
{{See also|List of Roman legions}}
[[File:Roman-legions-212-AD-Centrici-site-Keilo-Jack.jpg|thumb|300px|Map of Roman legions by 212 AD<ref>{{cite web|url=http://f.hypotheses.org/wp-content/blogs.dir/1447/files/2014/05/Roman-legions-212-AD-Centrici-site-Keilo-Jack.jpg |title=Map |website=.hypotheses.org}}</ref>]]

In the [[Later Roman Empire]], the number of legions was increased and the [[Campaign history of the Roman military|Roman army]] expanded. There is no evidence to suggest that legions changed in form before the [[Tetrarchy]], although there is evidence that they were smaller than the paper strengths usually quoted. The final form of the legion originated with the elite ''legiones palatinae'' created by [[Diocletian]] and the Tetrarchs. These were infantry units of around 1,000 men rather than the 5,000, including cavalry, of the old legions. The earliest ''legiones palatinae'' were the ''Lanciarii'', ''Joviani'', ''[[Jovians and Herculians|Herculiani]]'' and ''Divitenses''.{{Citation needed|date=October 2020}}

The 4th century saw a very large number of new, small legions created, a process which began under [[Constantine II (emperor)|Constantine II]]. In addition to the elite ''[[Palatini (Roman military)|palatini]]'', other legions called ''[[comitatenses]]'' and ''[[pseudocomitatenses]]'', along with the ''[[auxilia palatina]]'', provided the infantry of late Roman armies. The ''[[Notitia Dignitatum]]'' lists 25 ''legiones palatinae'', 70 ''legiones comitatenses'', 47 ''legiones pseudocomitatenses'' and 111 ''auxilia palatina'' in the field armies, and a further 47 ''legiones'' in the frontier armies.<ref>Totals from summary of Notitia Dignitatum in Richardot, Philippe, ''La fin de l'armée romaine 284–476'' [3rd ed.] Economica, 2005. {{ISBN|2717848614}}.</ref> Legion names such as ''[[Honorius (emperor)|Honoriani]]'' and ''[[Gratian]]enses'' found in the ''Notitia'' suggest that the process of creating new legions continued through the 4th century rather than being a single event. The names also suggest that many new legions were formed from ''[[vexillatio]]nes'' or from old legions. In addition, there were 24 vexillationes palatini, 73 ''vexillationes comitatenses''; 305 other units in the Eastern ''limitanei'' and 181 in the Western ''limitanei''.<ref>Jones, Later Roman Empire, pp. 1449–1450</ref> A rare instance of apparent direct continuity between the legions of the early Empire and those of the post-6th century army was ''Legion V Macedonica''; created in 43 BC, recorded in the ''Notitia Dignitatum'' as a ''legione comitatense'' under the title of ''Quinta Macedonica'' and surviving in Egypt until the Arab conquest of 637 AD.<ref>{{cite book|first=Gabriele|last=Esposito|page=77|title=The Late Roman Army|date=2016|publisher=Winged Hussar |isbn=978-0996365796}}</ref>

According to the late Roman writer [[Vegetius]]' ''[[De re militari]]'', each century had a [[ballista]] and each cohort had an [[Onager (weapon)|onager]], giving the legion a formidable siege train of 59 ballistae and 10 onagers, each manned by 10 ''libritors'' (artillerymen) and mounted on wagons drawn by oxen or mules. In addition to attacking cities and fortifications, these would be used to help defend Roman forts and fortified camps (''castra'') as well. They would even be employed on occasion, especially in the later Empire, as [[field artillery]] during battles or in support of river crossings.

Despite a number of organisational changes, the legion system survived the [[fall of the Western Roman Empire]]. It was continued within the [[Byzantine Empire|Eastern Roman Empire]] until the 7th century, when reforms begun by Emperor [[Heraclius]] to supply the increasing need for soldiers resulted in the [[Theme (Byzantine district)|Theme system]]. Despite this, the Eastern Roman armies continued to be influenced by the earlier Roman legions, and were maintained with similar levels of discipline, strategic prowess, and organization.