Augustus of the Eastern Roman Empire
Istanbul - Museo archeol. - Diocleziano (284-305 d.C.) - Foto G. Dall'Orto 28-5-2006.jpg
Laureate head of Diocletian
Emperor of the Roman Empire
Reign20 November 284 – 1 April 286 (in competition with Carinus until July 285)[1]
Reign1 April 286 – 1 May 305 (as Senior Augustus, ruled in the east)[2]
SuccessorConstantius Chlorus and Galerius
Co-emperorMaximian (Western Emperor)
Bornc. 22 December 244[3]
Salona (now Solin, Croatia)
Died3 December 311 (age 66)[4]
Aspalathos (now Split, Croatia)
Diocletian's Palace in Aspalathos. His tomb was later turned into a Christian church, the Cathedral of St. Domnius, which is still standing within the palace at Split.
Full name
Regnal name
Imperator Caesar Gaius Aurelius Valerius Diocletianus Augustus[5]

Diocletian (ən/; Latin: Gaius Aurelius Valerius Diocletianus Augustus), born Diocles (22 December 244 – 3 December 311),[4][6] was a Roman emperor from 284 to 305. Born to a family of low status in Dalmatia, Diocletian rose through the ranks of the military to become Roman cavalry commander to the Emperor Carus. After the deaths of Carus and his son Numerian on campaign in Persia, Diocletian was proclaimed emperor. The title was also claimed by Carus' surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.

Diocletian's reign stabilized the empire and marks the end of the Crisis of the Third Century. He appointed fellow officer Maximian as Augustus, co-emperor, in 286. Diocletian reigned in the Eastern Empire, and Maximian reigned in the Western Empire. Diocletian delegated further on 1 March 293, appointing Galerius and Constantius as Caesars, junior co-emperors, under himself and Maximian respectively. Under this 'tetrarchy', or "rule of four", each emperor would rule over a quarter-division of the empire. Diocletian secured the empire's borders and purged it of all threats to his power. He defeated the Sarmatians and Carpi during several campaigns between 285 and 299, the Alamanni in 288, and usurpers in Egypt between 297 and 298. Galerius, aided by Diocletian, campaigned successfully against Sassanid Persia, the empire's traditional enemy. In 299 he sacked their capital, Ctesiphon. Diocletian led the subsequent negotiations and achieved a lasting and favourable peace.

Diocletian separated and enlarged the empire's civil and military services and reorganized the empire's provincial divisions, establishing the largest and most bureaucratic government in the history of the empire. He established new administrative centres in Nicomedia, Mediolanum, Sirmium, and Trevorum, closer to the empire's frontiers than the traditional capital at Rome. Building on third-century trends towards absolutism, he styled himself an autocrat, elevating himself above the empire's masses with imposing forms of court ceremonies and architecture. Bureaucratic and military growth, constant campaigning, and construction projects increased the state's expenditures and necessitated a comprehensive tax reform. From at least 297 on, imperial taxation was standardized, made more equitable, and levied at generally higher rates.

Not all of Diocletian's plans were successful: the Edict on Maximum Prices (301), his attempt to curb inflation via price controls, was counterproductive and quickly ignored. Although effective while he ruled, Diocletian's tetrarchic system collapsed after his abdication under the competing dynastic claims of Maxentius and Constantine, sons of Maximian and Constantius respectively. The Diocletianic Persecution (303–312), the empire's last, largest, and bloodiest official persecution of Christianity, failed to eliminate Christianity in the empire; indeed, after 324, Christianity became the empire's preferred religion under Constantine. Despite these failures and challenges, Diocletian's reforms fundamentally changed the structure of Roman imperial government and helped stabilize the empire economically and militarily, enabling the empire to remain essentially intact for another 150 years despite being near the brink of collapse in Diocletian's youth. Weakened by illness, Diocletian left the imperial office on 1 May 305, and became the first Roman emperor to abdicate the position voluntarily. He lived out his retirement in his palace on the Dalmatian coast, tending to his vegetable gardens. His palace eventually became the core of the modern-day city of Split in Croatia.

Early life

Panorama of amphitheatre in Salona

Diocletian was born near Salona in Dalmatia (Solin in modern Croatia), some time around 244.[3] His parents gave him the Greek name Diocles, or possibly Diocles Valerius.[7] The modern historian Timothy Barnes takes his official birthday, 22 December, as his actual birthdate. Other historians are not so certain.[8] His parents were of low status; Eutropius records "that he is said by most writers to have been the son of a scribe, but by some to have been a freedman of a senator called Anulinus." The first forty years of his life are mostly obscure.[9] The Byzantine chronicler Joannes Zonaras states that he was Dux Moesiae,[10] a commander of forces on the lower Danube.[11] The often-unreliable Historia Augusta states that he served in Gaul, but this account is not corroborated by other sources and is ignored by modern historians of the period.[12] The first time Diocletian's whereabouts are accurately established, in 282, the Emperor Carus made him commander of the Protectores domestici, the elite cavalry force directly attached to the Imperial household – a post that earned him the honour of a consulship in 283.[13] As such, he took part in Carus' subsequent Persian campaign.

Death of Numerian

Carus's death, amid a successful war with Persia and in mysterious circumstances[14] – he was believed to have been struck by lightning or killed by Persian soldiers[15] – left his sons Numerian and Carinus as the new Augusti. Carinus quickly made his way to Rome from his post in Gaul as imperial commissioner and arrived there by January 284, becoming legitimate Emperor in the West. Numerian lingered in the East.[16] The Roman withdrawal from Persia was orderly and unopposed.[17] The Sassanid king Bahram II could not field an army against them as he was still struggling to establish his authority. By March 284, Numerian had only reached Emesa (Homs) in Syria; by November, only Asia Minor.[18] In Emesa he was apparently still alive and in good health: he issued the only extant rescript in his name there,[19][Note 1] but after he left the city, his staff, including the prefect (Numerian's father-in-law, and as such the dominant influence in the Emperor's entourage)[21] Aper, reported that he suffered from an inflammation of the eyes. He travelled in a closed coach from then on.[22] When the army reached Bithynia,[16] some of the soldiers smelled an odor emanating from the coach.[17] They opened its curtains and inside they found Numerian dead.[23] Both Eutropius and Aurelius Victor describe Numerian's death as an assassination.[24]

Aper officially broke the news in Nicomedia (İzmit) in November.[25] Numerianus' generals and tribunes called a council for the succession, and chose Diocles as Emperor,[26] in spite of Aper's attempts to garner support.[25] On 20 November 284, the army of the east gathered on a hill 5 kilometres (3.1 mi) outside Nicomedia. The army unanimously saluted Diocles as their new Augustus, and he accepted the purple imperial vestments. He raised his sword to the light of the sun and swore an oath disclaiming responsibility for Numerian's death. He asserted that Aper had killed Numerian and concealed it.[27] In full view of the army, Diocles drew his sword and killed Aper.[28] According to the Historia Augusta, he quoted from Virgil while doing so.[29] Soon after Aper's death, Diocles changed his name to the more Latinate "Diocletianus"[30]--in full, Gaius Aurelius Valerius Diocletianus.[31]

Conflict with Carinus

After his accession, Diocletian and Lucius Caesonius Bassus[32] were named as consuls and assumed the fasces in place of Carinus and Numerianus.[33] Bassus was a member of a senatorial family from Campania, a former consul and proconsul of Africa, chosen by Probus for signal distinction.[34] He was skilled in areas of government where Diocletian presumably had no experience.[25] Diocletian's elevation of Bassus as consul symbolized his rejection of Carinus' government in Rome, his refusal to accept second-tier status to any other emperor,[34] and his willingness to continue the long-standing collaboration between the empire's senatorial and military aristocracies.[25] It also tied his success to that of the Senate, whose support he would need in his advance on Rome.[34]

Diocletian was not the only challenger to Carinus' rule; the usurper M. Aurelius Julianus, Carinus' corrector Venetiae, took control of northern Italy and Pannonia after Diocletian's accession.[35] Julianus minted coins from the mint at Siscia (Sisak, Croatia) declaring himself emperor and promising freedom. It was all good publicity for Diocletian, and it aided in his portrayal of Carinus as a cruel and oppressive tyrant.[36] Julianus' forces were weak, however, and were handily dispersed when Carinus' armies moved from Britain to northern Italy. As leader of the united East, Diocletian was clearly the greater threat.[37] Over the winter of 284–85, Diocletian advanced west across the Balkans. In the spring, some time before the end of May,[38] his armies met Carinus' across the river Margus (Great Morava) in Moesia. In modern accounts, the site has been located between the Mons Aureus (Seone, west of Smederevo) and Viminacium,[34] near modern Belgrade, Serbia.[39]

Despite having the stronger, more powerful army, Carinus held the weaker position. His rule was unpopular, and it was later alleged that he had mistreated the Senate and seduced his officers' wives.[40] It is possible that Flavius Constantius, the governor of Dalmatia and Diocletian's associate in the household guard, had already defected to Diocletian in the early spring.[41] When the Battle of the Margus began, Carinus' prefect Aristobulus also defected.[25] In the course of the battle, Carinus was killed by his own men. Following Diocletian's victory, both the western and the eastern armies acclaimed him as Emperor.[42] Diocletian exacted an oath of allegiance from the defeated army and departed for Italy.[43]

Other Languages
Afrikaans: Diocletianus
العربية: ديوكلتيانوس
aragonés: Dioclecián
asturianu: Diocleciano
azərbaycanca: Diokletian
تۆرکجه: دیوکلسین
Bân-lâm-gú: Diocletianus
беларуская: Дыяклетыян
български: Диоклециан
bosanski: Dioklecijan
brezhoneg: Diocletianus
català: Dioclecià
čeština: Diocletianus
Cymraeg: Diocletian
dansk: Diocletian
Deutsch: Diokletian
Ελληνικά: Διοκλητιανός
español: Diocleciano
Esperanto: Diokleciano
euskara: Diokleziano
فارسی: دیوکلسین
français: Dioclétien
galego: Diocleciano
贛語: 底厄勒斯
հայերեն: Դիոկղետիանոս
hrvatski: Dioklecijan
Bahasa Indonesia: Diokletianus
íslenska: Diocletianus
italiano: Diocleziano
ქართული: დიოკლეტიანე
Kiswahili: Diokletian
Latina: Diocletianus
latviešu: Diokletiāns
lietuvių: Diokletianas
македонски: Диоклецијан
മലയാളം: ഡയക്ലീഷൻ
Bahasa Melayu: Diocletian
Nederlands: Diocletianus
norsk: Diokletian
occitan: Dioclecian
oʻzbekcha/ўзбекча: Diokletian
polski: Dioklecjan
português: Diocleciano
română: Dioclețian
русский: Диоклетиан
Scots: Diocletian
sicilianu: Diuclezzianu
Simple English: Diocletian
slovenčina: Dioklecián
slovenščina: Dioklecijan
српски / srpski: Диоклецијан
srpskohrvatski / српскохрватски: Dioklecijan
svenska: Diocletianus
Tagalog: Diocleciano
Türkçe: Diocletianus
українська: Діоклетіан
Tiếng Việt: Diocletianus
Winaray: Diocletian
吴语: 戴克里先
Yorùbá: Diocletian
粵語: 戴克里先
Zazaki: Diocletianus
中文: 戴克里先