Editing Diocletian (section)

===Military===
{{See also|Late Roman army#Diocletian|l1=Late Roman army: Diocletian}}[[File:Bust of Diocletian at the National Museum of Serbia (cropped).jpg|thumb|Bust labelled as Diocletian at the [[National Museum of Serbia]]|218x218px]]It is archaeologically difficult to distinguish Diocletian's fortifications from those of his successors and predecessors. The [[Devil's Dykes]], for example—the Danubian earthworks traditionally attributed to Diocletian—cannot even be securely dated to a particular century. The most that can be said about built structures under Diocletian's reign is that he rebuilt and strengthened forts at the Upper Rhine frontier (where he followed the works built under [[Marcus Aurelius Probus|Probus]] along the [[Lake Constance]]-[[Basel]] and the Rhine–[[Iller]]–Danube line),{{sfn|Carrié|Rousselle|1999|p=166}} on the Danube (where a new line of forts on the far side of the river, the ''Ripa Sarmatica'', was added to older, rehabilitated fortresses),<ref name="Luttwak">{{cite book |last=Luttwak |first=Edward |year=1979 |title=The Grand Strategy of the Roman Empire |publisher=[[Johns Hopkins University Press]] |location=Baltimore |isbn=0-8018-2158-4 |page=176 }}</ref> in Egypt and on the frontier with Persia. Beyond that, much discussion is speculative and reliant on the broad generalizations of written sources. Diocletian and the tetrarchs had no consistent plan for frontier advancement, and records of raids and forts built across the frontier are likely to indicate only temporary claims. The ''[[Strata Diocletiana]]'', built after the Persian Wars, which ran from the Euphrates North of Palmyra and South towards northeast Arabia in the general vicinity of [[Bostra]], is the classic Diocletianic frontier system, consisting of an outer road followed by tightly spaced forts&nbsp;– defensible hard-points manned by small garrisons&nbsp;– followed by further fortifications in the rear.<ref name="Luttwak" />{{sfnm|1a1=CAH|1pp=124–126|2a1=Southern|2y=2001|2pp=154–155|3a1=Rees|3y=2004|3p=19–20|4a1=Williams|4y=1985|4pp=91–101}} In an attempt to resolve the difficulty and slowness of transmitting orders to the frontier, the new capitals of the tetrarchic era were all much closer to the empire's frontiers than Rome had been:{{sfnm|1a1=CAH|1p=171|2a1=Rees|2y=2004|2p=27}} Trier sat on the [[Moselle]], a [[tributary]] of the Rhine, Sirmium and Serdica were close to the Danube, Thessaloniki was on the route leading eastward, and Nicomedia and Antioch were important points in dealings with Persia.{{sfn|Rees|2004|p=27}}

Lactantius criticized Diocletian for an excessive increase in troop sizes, declaring that "each of the four princes strove to maintain a much more considerable military force than any sole emperor had done in times past. There began to be fewer men who paid taxes than there were who received wages; so that the means of the husbandmen being exhausted by enormous impositions, the farms were abandoned, cultivated grounds became woodland, and universal dismay prevailed".{{sfn|Lactantius|loc=7}} The fifth-century pagan [[Zosimus (historian)|Zosimus]], by contrast, praised Diocletian for keeping troops on the borders, rather than keeping them in the cities, as Constantine was held to have done.{{sfn|Corcoran|2006|p=46; quoting [[Zosimus (historian)|Zosimus]], [https://www.tertullian.org/fathers/zosimus02_book2.htm 2.34]}} Both these views had some truth to them, despite the biases of their authors: Diocletian and the tetrarchs did greatly expand the army, and the growth was mostly in frontier regions, where the increased effectiveness of the new Diocletianic legions seem to have been mostly spread across a network of strongholds.{{sfn|Christol|Nony|2003|p=241}} Nevertheless, it is difficult to establish the precise details of these shifts given the weakness of the sources.{{sfn|Southern|2001|p=157}}{{sfn|Treadgold|1997|p=19}} The army expanded to about 580,000 men from a 285 strength of 390,000, of which 310,000 men were stationed in the East, most of whom manned the Persian frontier. The navy increased from approximately 45,000 to approximately 65,000 men.{{sfn|Treadgold|1997|p=19}}{{refn|The 6th-century author [[John the Lydian]] provides extraordinarily precise troop numbers: 389,704 in the army and 45,562 in the navy.<ref>''[https://www.roger-pearse.com/weblog/wp-content/uploads/2017/12/John-Lydus-On-the-Months-tr.-Hooker-2nd-ed.-2017-1.pdf De Mensibus] {{Webarchive|url=https://web.archive.org/web/20230304225750/https://www.roger-pearse.com/weblog/wp-content/uploads/2017/12/John-Lydus-On-the-Months-tr.-Hooker-2nd-ed.-2017-1.pdf |date=4 March 2023 }}'' 1.27.</ref> His precision has polarized modern historians. Some believe that Lydus found these figures in official documents and that they are therefore broadly accurate; others believe that he fabricated them.{{sfn|Rees|2004|p=17}}|group="Note"}}

Diocletian's expansion of the army and civil service meant that the empire's tax burden grew. Since military upkeep took the largest portion of the imperial budget, any reforms here would be especially costly. The proportion of the adult male population, excluding slaves, serving in the army increased from roughly 1 in 25 to 1 in 15, an increase judged excessive by some modern commentators. Official troop allowances were kept to low levels, and the mass of troops often resorted to extortion or the taking of civilian jobs. Arrears became the norm for most troops. Many were even given payment in kind in place of their salaries. Were he unable to pay for his enlarged army, there would likely be civil conflict, potentially open revolt. Diocletian was led to devise a new system of taxation.{{sfnm|1a1=Southern|1y=2001|1pp=158–159|2a1=Treadgold|2y=1997|2pp=112–113}}