Roman emperor from 284 to 305
This article is about the Roman emperor. For other uses, see Diocletian (disambiguation).
Diocletian (DYE-ə-KLEE-shən; Latin: Gaius Aurelius Valerius Diocletianus; Ancient Greek: Διοκλητιανός, romanized: Diokletianós; 242/245 – 311/312), nicknamed Jovius, was Roman emperor from 284 until his abdication in 305. He was born Diocles to a family of low status in the Roman province of Dalmatia. Diocles rose through the ranks of the military early in his career, eventually becoming a cavalry commander for the army of Emperor Carus. After the deaths of Carus and his son Numerian on a campaign in Persia, Diocles was proclaimed emperor by the troops, taking the name Diocletianus. The title was also claimed by Carus's surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.
Diocletian's reign stabilized the empire and ended the Crisis of the Third Century. He initiated the process of the Roman Empire split and 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 junior colleagues (each with the title Caesar), under himself and Maximian respectively. Under the Tetrarchy, or "rule of four", each tetrarch 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 Persia, the empire's traditional enemy, and in 299, he sacked their capital, Ctesiphon. Diocletian led the subsequent negotiations and achieved a lasting and favorable 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 centers 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. After 324, Christianity became the empire's preferred religion under Constantine. Despite these failures and challenges, Diocletian's reforms fundamentally changed the structure of the 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, becoming 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.
Diocletian was born in Dalmatia, probably at or near the town of Salona (modern Solin, Croatia), to which he retired later in life. His original name was Diocles (in full, Gaius Valerius Diocles),[4] possibly derived from Dioclea, the name of both his mother and her supposed place of birth. Diocletian's official birthday was 22 December, and his year of birth has been estimated at between 242 and 245 based on a statement that he was aged 68 at death (alongside other evidence). 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. Diocletian was considered an Illyricianus (Illyrian) who had been schooled and promoted by Aurelian.[8] The 12th-century Byzantine chronicler Joannes Zonaras states that he was DuxMoesiae, a commander of forces on the lower Danube. The often-unreliable Historia Augusta states that he served in Gaul, but this is not corroborated by other sources and is ignored by modern historians. The first time Diocletian's whereabouts are accurately established was in 282 when the Emperor Carus made him commander of the Protectores domestici, the elite cavalry force directly attached to the Imperial household. This post earned him the honor of a consulship in 283.
Carus's death, amid a successful war with Persia and in mysterious circumstances – he was believed to have been struck by lightning or killed by Persian soldiers[14][15] – left his sons Numerian and Carinus as the new Augusti. Carinus quickly made his way to Rome from his post in Gaul and arrived there by January 284, becoming the legitimate Emperor in the West. Numerian lingered in the East. The Roman withdrawal from Persia was orderly and unopposed. 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. In Emesa he was apparently still alive and in good health: he issued the only extant rescript in his name there,[Note 2] but after he left the city, his staff, including the prefect (Numerian's father-in-law and the dominant influence in his entourage)Aper, reported that he suffered from an inflammation of the eyes. He traveled in a closed coach from then on. When the army reached Bithynia, some of the soldiers smelled an odor emanating from the coach. They opened its curtains and found Numerian dead. Both Eutropius and Aurelius Victor describe Numerian's death as an assassination.
Aper officially broke the news in Nicomedia (İzmit) in November. Numerian's generals and tribunes called a council for the succession, and chose Diocles as Emperor, in spite of Aper's attempts to garner support. 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. In full view of the army, Diocles drew his sword and killed Aper. Soon after Aper's death, Diocles changed his name to the more Latinate "Diocletianus" – in full, Gaius Valerius Diocletianus.[4][Note 3]
After his accession, Diocletian and Lucius Caesonius Bassus were named as consuls and assumed the fasces in place of Carinus and Numerian. Bassus was a member of a senatorial family from Campania, a former consul and proconsul of Africa, chosen by Probus for signal distinction. He was skilled in areas of government where Diocletian presumably had no experience. Diocletian's elevation of Bassus symbolized his rejection of Carinus' government in Rome, his refusal to accept second-tier status to any other emperor, and his willingness to continue the long-standing collaboration between the empire's senatorial and military aristocracies. It also tied his success to that of the Senate, whose support he would need in his advance on Rome.
Diocletian was not the only challenger to Carinus' rule; the usurper Julianus, Carinus' corrector Venetiae, took control of northern Italy and Pannonia after Diocletian's accession. Julianus minted coins from Siscia (Sisak, Croatia) declaring himself emperor and promising freedom. This aided Diocletian in his portrayal of Carinus as a cruel and oppressive tyrant. Julianus' forces were weak, and were handily dispersed when Carinus' armies moved from Britain to northern Italy. As the leader of the united East, Diocletian was clearly the greater threat. Over the winter of 284–85, Diocletian advanced west across the Balkans. In the spring, some time before the end of May, 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, near modern Belgrade, Serbia.
Despite having a 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. 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. When the Battle of the Margus began, Carinus' prefect Aristobulus also defected. 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. Diocletian exacted an oath of allegiance from the defeated army and departed for Italy.
Diocletian may have become involved in battles against the Quadi and Marcomanni immediately after the Battle of the Margus. He eventually made his way to northern Italy and made an imperial government, but it is not known whether he visited Rome at this time. There is a contemporary issue of coins suggestive of an imperial adventus (arrival) for the city,[42] but some modern historians state that Diocletian avoided the city, to demonstrate that the city and its Senate were no longer politically relevant to the affairs of the empire. Diocletian dated his reign from his elevation by the army, not his ratification by the Senate, following the practice established by Carus, who had declared the Senate's ratification a useless formality. Diocletian offered proof of his deference towards the Senate by retaining Aristobulus as ordinary consul and colleague for 285 (one of the few instances during the Late Empire in which an emperor admitted a privatus as his colleague)[47] and by creating senior senators Vettius Aquilinus and Junius Maximus ordinary consuls for the following year – for Maximus, it was his second consulship.
If Diocletian did enter Rome shortly after his accession, he did not stay long; he is attested back in the Balkans by 2 November 285, on campaign against the Sarmatians.
Diocletian replaced the prefect of Rome with his consular colleague Bassus. Most officials who had served under Carinus retained their offices under Diocletian. In an act of clementia denoted by the epitomator of Aurelius Victor as unusual, Diocletian did not kill or depose Carinus's traitorous praetorian prefect and consul Aristobulus, but confirmed him in both roles. He later gave him the proconsulate of Africa and the post of urban prefect for 295. The other figures who retained their offices might have also betrayed Carinus.
The assassinations of Aurelian and Probus demonstrated that sole rulership was dangerous to the stability of the empire. Conflict boiled in every province, from Gaul to Syria, Egypt to the lower Danube. It was too much for one person to control, and Diocletian needed a lieutenant. According to Eutropius,[Note 4] Diocletian raised his fellow-officer Maximian to the office of Caesar, making him his heir and effective co-ruler.
The concept of dual rulership was not new to the Roman Empire. Augustus, the first emperor, had nominally shared power with his colleagues, and a formal office of co-emperor (co-Augustus) had existed from Marcus Aurelius onward. Most recently, Emperor Carus and his sons had ruled together, albeit unsuccessfully. Diocletian was in a less comfortable position than most of his predecessors, as he had a daughter, Valeria, but no sons. His co-ruler had to be from outside his family, raising the question of trust. Some historians state that Diocletian adopted Maximian as his filius Augusti, his "Augustan son", upon his appointment to the throne, following the precedent of some previous Emperors. This argument has not been universally accepted. Diocletian and Maximian added each other's nomina (their family name, "Valerius" and "Aurelius", respectively) to their own, thus creating an artificial family link and becoming part of the "Aurelius Valerius" family.[4]
The relationship between Diocletian and Maximian was quickly couched in religious terms. Around 287 Diocletian assumed the title Iovius (Jovius), and Maximian assumed the title Herculius (Hercules). The titles were probably meant to convey certain characteristics of their associated leaders. Diocletian, in Jovian style, would take on the dominating roles of planning and commanding; Maximian, in Herculian mode, would act as Jupiter's heroic subordinate. For all their religious connotations, the emperors were not "gods" in the tradition of the Imperial cult – although they may have been hailed as such in Imperial panegyrics. Instead, they were seen as the gods' representatives, effecting their will on earth. The shift from military acclamation to divine sanctification took the power to appoint emperors away from the army. Religious legitimization elevated Diocletian and Maximian above potential rivals in a way military power and dynastic claims could not.
After his acclamation, Maximian was dispatched to fight the rebel Bagaudae, insurgent peasants of Gaul. Diocletian returned to the East, progressing slowly. By 2 November, he had only reached Civitas Iovia (Botivo, near Ptuj, Slovenia).[68] In the Balkans during the autumn of 285, he encountered a tribe of Sarmatians who demanded assistance. The Sarmatians requested that Diocletian either help them recover their lost lands or grant them pasturage rights within the empire. Diocletian refused and fought a battle with them, but was unable to secure a complete victory. The nomadic pressures of the European Plain remained and could not be solved by a single war; soon the Sarmatians would have to be fought again.
Diocletian wintered in Nicomedia.[Note 5] There may have been a revolt in the eastern provinces at this time, as he brought settlers from Asia to populate emptied farmlands in Thrace. He visited Syria Palaestina the following spring, [Note 6] His stay in the East saw diplomatic success in the conflict with Persia: in 287, Bahram II granted him precious gifts, declared open friendship with the Empire, and invited Diocletian to visit him. Roman sources insist that the act was entirely voluntary.
Around the same time, perhaps in 287, Persia relinquished claims on Armenia and recognized Roman authority over territory to the west and south of the Tigris. The western portion of Armenia was incorporated into the empire and made a province. Tiridates III, the Arsacid claimant to the Armenian throne and a Roman client, had been disinherited and forced to take refuge in the empire after the Persian conquest of 252–53. In 287, he returned to lay claim to the eastern half of his ancestral domain and encountered no opposition. Bahram II's gifts were widely recognized as symbolic of a victory in the ongoing conflict with Persia, and Diocletian was hailed as the "founder of eternal peace". The events might have represented a formal end to Carus's eastern campaign, which probably ended without an acknowledged peace. At the conclusion of discussions with the Persians, Diocletian re-organized the Mesopotamian frontier and fortified the city of Circesium (Buseire, Syria) on the Euphrates.
Maximian's campaigns were not proceeding as smoothly. The Bagaudae had been easily suppressed, but Carausius, the man he had put in charge of operations against Saxon and Frankishpirates on the Saxon Shore, had, according to literary sources, begun keeping the goods seized from the pirates for himself. Maximian issued a death warrant for his larcenous subordinate. Carausius fled the Continent, proclaimed himself emperor, and agitated Britain and northwestern Gaul into open revolt against Maximian and Diocletian.
Far more probable, according to the archaeological evidence, is that Carausius had held some important military post in Britain, already had a firm basis of power in Britain and Northern Gaul, and profited from the lack of legitimacy of the central government. Carausius strove to have his legitimacy as a junior emperor acknowledged by Diocletian: in his coinage, he extolled the "concord" between him and the central power. One bronze piece from 290 read PAX AVGGG, "the Peace of the three Augusti"; on the other side, it showed Carausius together with Diocletian and Maximian, with the caption CARAVSIVS ET FRATRES SVI, "Carausius & his brothers".[87] Diocletian could not allow a breakaway regional usurper following in Postumus's footprints to enter, of his own accord, the imperial college.
Spurred by the crisis, on 1 April 286,[Note 4] Maximian took up the title of Augustus (emperor). Unusually, Diocletian could not have been present to witness it. It has even been suggested that Maximian usurped the title and was only later recognized by Diocletian in hopes of avoiding civil war. This suggestion is unpopular, as it is clear that Diocletian meant for Maximian to act with a certain amount of independence. It may be posited that Diocletian felt the need to bind Maximian closer to him, by making him his empowered associate, to avoid the possibility of him striking some sort of deal with Carausius.
Maximian realized that he could not immediately suppress the rogue commander, so in 287 he campaigned against tribes beyond the Rhine instead. As Carausius was allied to the Franks, Maximian's campaigns could be seen as an effort to deny him a basis of support on the mainland. The following spring, as Maximian prepared a fleet for an expedition against Carausius, Diocletian returned from the East to meet Maximian. The two emperors agreed on a joint campaign against the Alamanni. Diocletian invaded Germania through Raetia while Maximian progressed from Mainz. Each burned crops and food supplies as he went, destroying the Germans' means of sustenance.[101] The two men added territory to the empire and allowed Maximian to continue preparations against Carausius without further disturbance. On his return to the East, Diocletian managed what was probably another rapid campaign against the resurgent Sarmatians. No details survive, but surviving inscriptions indicate that Diocletian took the title Sarmaticus Maximus after 289.
In the East, Diocletian engaged in diplomacy with desert tribes in the regions between Rome and Persia. He might have been attempting to persuade them to ally themselves with Rome, thus reviving the old, Rome-friendly, Palmyrenesphere of influence, or to reduce the frequency of their incursions. No details survive for these events. Some of the princes of these states were Persian client kings, a disturbing fact for the Romans in light of increasing tensions with the Sassanids. In the West, Maximian lost the fleet built in 288 and 289, probably in the early spring of 290. The panegyrist who refers to the loss suggests that its cause was a storm,[109] but this might have been an attempt to conceal an embarrassing military defeat. Diocletian broke off his tour of the Eastern provinces soon thereafter. He returned with haste to the West, reaching Emesa by 10 May 290, and Sirmium on the Danube by 1 July 290.
Diocletian met Maximian in Milan either in late December 290 or January 291. The meeting was undertaken with a sense of solemn pageantry. The emperors spent most of their time in public appearances. It has been surmised that the ceremonies were arranged to demonstrate Diocletian's continuing support for his faltering colleague. A deputation from the Roman Senate met with the emperors, renewing its infrequent contact with the Imperial office.[117] The choice of Milan over Rome further snubbed the capital's pride. But then it was already a long-established practice that Rome itself was only a ceremonial capital, as the actual seat of the Imperial administration was determined by the needs of defense. Long before Diocletian, Gallienus (r. 253–68) had chosen Milan for his headquarters. If the panegyric detailing the ceremony implied that the true center of the empire was not Rome, but where the emperor sat ("...the capital of the empire appeared to be there, where the two emperors met"), it simply echoed what had already been stated by the historian Herodian in the early third century: "Rome is where the emperor is". During the meeting, decisions on matters of politics and war were probably made in secret. The Augusti would not meet again until 303.
See also: Tetrarchy
Some time after his return, and before 293, Diocletian transferred command of the war against Carausius from Maximian to Flavius Constantius, who concluded it successfully in 296. Constantius was a former governor of Dalmatia and a man of military experience stretching back to Aurelian's campaigns against Zenobia (272–73). He was Maximian's praetorian prefect in Gaul, and the husband to Maximian's daughter, Theodora. On 1 March 293 at Milan, Maximian gave Constantius the office of Caesar. The same day, in either Philippopolis (Plovdiv, Bulgaria) or Sirmium, Diocletian did the same for Galerius, husband to Diocletian's daughter Valeria, and perhaps Diocletian's praetorian prefect.[Note 7] Constantius was assigned Gaul and Britain. Galerius was initially assigned Syria, Palestine, Egypt, and responsibility for the eastern borderlands.
This arrangement is called the Tetrarchy, from a Greek term meaning "rulership by four". The Tetrarchs were more or less sovereign in their own lands, and they travelled with their own imperial courts, administrators, secretaries, and armies. They were joined by blood and marriage; Diocletian and Maximian now styled themselves as brothers, and formally adopted Galerius and Constantius as sons. These relationships implied a line of succession. Galerius and Constantius would become Augusti after the departure of Diocletian and Maximian. Maximian's son Maxentius and Constantius's son Constantine would then become Caesars. In preparation for their future roles, Constantine and Maxentius were taken to Diocletian's court in Nicomedia.
Diocletian spent the spring of 293 travelling with Galerius from Sirmium (Sremska Mitrovica, Serbia) to Byzantium (Istanbul, Turkey). Diocletian then returned to Sirmium, where he remained for the following winter and spring. He campaigned successfully against the Sarmatians in 294, probably in the autumn. The Sarmatians' defeat kept them from the Danube provinces for a long time. Meanwhile, Diocletian built forts north of the Danube, part of a new defensive line called the Ripa Sarmatica, at Aquincum (Budapest, Hungary), Bononia (Vidin, Bulgaria), Ulcisia Vetera, Castra Florentium, Intercisa (Dunaújváros, Hungary), and Onagrinum (Begeč, Serbia). In 295 and 296 Diocletian campaigned in the region again, and won a victory over the Carpi in the summer of 296. Later during both 299 and 302, as Diocletian was residing in the East, it was Galerius's turn to campaign victoriously on the Danube. By the end of his reign, Diocletian had secured the entire length of the Danube, provided it with forts, bridgeheads, highways, and walled towns, and sent fifteen or more legions to patrol the region; an inscription at Sexaginta Prista on the Lower Danube extolled restored tranquility to the region. The defense came at a heavy cost but was a significant achievement in an area difficult to defend.
Galerius, meanwhile, was engaged during 291–293 in disputes in Upper Egypt, where he suppressed a regional uprising. He returned to Syria in 295 to fight the revanchist Persian empire. Diocletian's attempts to bring the Egyptian tax system in line with Imperial standards stirred discontent, and a revolt swept the region after Galerius's departure. The usurper Domitius Domitianus declared himself Augustus in July or August 297. Much of Egypt, including Alexandria, recognized his rule. Diocletian moved into Egypt to suppress him, first putting down rebels in the Thebaid in the autumn of 297, then moving on to besiege Alexandria. Domitianus died in December 297, by which time Diocletian had secured control of the Egyptian countryside. Alexandria, whose defense was organized under Domitianus's former correctorAurelius Achilleus, held out probably until March 298. Later in 298, the triumphal column now known as Pompey's Pillar was erected in Alexandria to honor Diocletian.
Bureaucratic affairs were completed during Diocletian's stay: a census took place, and Alexandria, in punishment for its rebellion, lost the ability to mint independently. Diocletian's reforms in the region, combined with those of Septimius Severus, brought Egyptian administrative practices much closer to Roman standards. Diocletian travelled south along the Nile the following summer, where he visited Oxyrhynchus and Elephantine. In Nubia, he made peace with the Nobatae and Blemmyes tribes. Under the terms of the peace treaty Rome's borders moved north to Philae and the two tribes received an annual gold stipend. Diocletian left Africa quickly after the treaty, moving from Upper Egypt in September 298 to Syria in February 299. He met with Galerius in Mesopotamia.
See also: Roman–Iranian relations and Roman–Persian Wars
In 294, Narseh, a son of Shapur who had been passed over for the Sassanid succession, came to power in Persia. In early 294, Narseh sent Diocletian the customary package of gifts between the empires, and Diocletian responded with an exchange of ambassadors. Within Persia, Narseh was destroying every trace of his immediate predecessors from public monuments. He sought to identify himself with the warlike kings Ardashir I (r. 226–241) and Shapur I (r. 241–272), who had defeated and imprisoned Emperor Valerian (r. 253–260) following his failed invasion of the Sasanian Empire.
Narseh declared war on Rome in 295 or 296. He appears to have first invaded western Armenia, where he seized the lands delivered to Tiridates in the peace of 287.[149] He moved south into Roman Mesopotamia in 297, where he inflicted a severe defeat on Galerius in the region between Carrhae (Harran, Turkey) and Callinicum (Raqqa, Syria), suggested by the historian Fergus Millar to have been somewhere on the Balikh River. Diocletian may or may not have been present at the battle, but he quickly divested himself of all responsibility. In a public ceremony at Antioch, the official version of events was clear: Galerius was responsible for the defeat; Diocletian was not. Diocletian publicly humiliated Galerius, forcing him to walk for a mile at the head of the Imperial caravan, still clad in the purple robes of the Emperor.[153][Note 8]
Galerius was reinforced, probably in the spring of 298, by a new contingent collected from the empire's Danubian holdings. Narseh did not advance from Armenia and Mesopotamia, leaving Galerius to lead the offensive in 298 with an attack on northern Mesopotamia via Armenia.[Note 9] It is unclear if Diocletian was present to assist the campaign; he might have returned to Egypt or Syria.[Note 10] Narseh retreated to Armenia to fight Galerius's force, putting himself at a disadvantage; the rugged Armenian terrain was favorable to Roman infantry, but not to Sassanid cavalry. In two battles, Galerius won major victories over Narseh. During the second encounter, Roman forces seized Narseh's camp, his treasury, his harem, and his wife. Galerius continued down the Tigris, and took the Persian capital Ctesiphon before returning to Roman territory along the Euphrates.
Narseh sent an ambassador to Galerius to plead for the return of his wives and children in the course of the war, but Galerius dismissed him. Serious peace negotiations began in the spring of 299. The magister memoriae (secretary) of Diocletian and Galerius, Sicorius Probus, was sent to Narseh to present terms. The conditions of the resulting Peace of Nisibis were heavy: Armenia returned to Roman domination, with the fort of Ziatha as its border; Caucasian Iberia would pay allegiance to Rome under a Roman appointee; Nisibis, now under Roman rule, would become the sole conduit for trade between Persia and Rome; and Rome would exercise control over the five satrapies between the Tigris and Armenia: Ingilene, Sophanene (Sophene), Arzanene (Aghdznik), Corduene (Carduene), and Zabdicene (near modern Hakkâri, Turkey). These regions included the passage of the Tigris through the Anti-Taurus range; the Bitlis pass, the quickest southerly route into Persian Armenia; and access to the Tur Abdin plateau.
A stretch of land containing the later strategic strongholds of Amida (Diyarbakır, Turkey) and Bezabde came under firm Roman military occupation. With these territories, Rome would have an advance station north of Ctesiphon, and would be able to slow any future advance of Persian forces through the region. Many cities east of the Tigris came under Roman control, including Tigranokert, Saird, Martyropolis, Balalesa, Moxos, Daudia, and Arzan – though under what status is unclear. At the conclusion of the peace, Tiridates regained both his throne and the entirety of his ancestral claim. Rome secured a wide zone of cultural influence, which led to a wide diffusion of Syriac Christianity from a center at Nisibis in later decades, and the eventual Christianization of Armenia.
To strengthen the defence of the east Diocletian had a fortified road constructed at the southern border, where the empire bordered the Arabs, in the year 300. This road would remain in use for centuries but proved ineffective in defending the border as conventional armies could not operate in the region.[168]
Further information: Diocletianic Persecution
At the conclusion of the Peace of Nisibis, Diocletian and Galerius returned to Antioch. At some time in 299, the emperors took part in a ceremony of sacrifice and divination in an attempt to predict the future. The haruspices were unable to read the entrails of the sacrificed animals and blamed Christians in the Imperial household. The emperors ordered all members of the court to perform a sacrifice to purify the palace. The emperors sent letters to the military command, demanding the entire army perform the required sacrifices or face discharge.[169][170] Diocletian was conservative in matters of religion, faithful to the traditional Roman pantheon and understanding of demands for religious purification, but Eusebius, Lactantius and Constantine state that it was Galerius, not Diocletian, who was the prime supporter of the purge. Galerius, even more devoted and passionate than Diocletian, saw political advantage in the persecution. He was willing to break with a government policy of inaction on the issue.
Antioch was Diocletian's primary residence from 299 to 302, while Galerius swapped places with his Augustus on the Middle and Lower Danube. Diocletian visited Egypt once, over the winter of 301–2, and issued a grain dole in Alexandria. Following some public disputes with Manicheans, Diocletian ordered that the leading followers of Mani be burnt alive along with their scriptures. In a 31 March 302 rescript from Alexandria, he declared that low-status Manicheans must be executed by the blade, and high-status Manicheans must be sent to work in the quarries of Proconnesus (Marmara Island, Turkey) or the mines of Phaeno in southern Palestine. All Manichean property was to be seized and deposited in the imperial treasury. Diocletian found much to be offended by in Manichean religion: its novelty, its alien origins, its perceived corruption of Roman morals, and its inherent opposition to long-standing religious traditions. His reasons for opposing Manichaeanism were also applied to his next target, Christianity.
Diocletian returned to Antioch in the autumn of 302. He ordered that the deaconRomanus of Caesarea have his tongue removed for defying the order of the courts and interrupting official sacrifices. Romanus was then sent to prison, where he was executed on 17 November 303. Diocletian left the city for Nicomedia in the winter, accompanied by Galerius. According to Lactantius, Diocletian and Galerius argued over imperial policy towards Christians while wintering at Nicomedia in 302. Diocletian believed that forbidding Christians from the bureaucracy and military would be sufficient to appease the gods, but Galerius pushed for extermination. The two men sought the advice of the oracle of Apollo at Didyma. The oracle responded that the impious on Earth hindered Apollo's ability to provide advice. Rhetorically Eusebius records the Oracle as saying "The just on Earth..."[182] These impious, Diocletian was informed by members of the court, could only refer to the Christians of the empire. At the behest of his court, Diocletian acceded to demands for universal persecution.
On 23 February 303, Diocletian ordered that the newly built church at Nicomedia be razed. He demanded that its scriptures be burned, and seized its precious stores for the treasury. The next day, Diocletian's first "Edict against the Christians" was published. The edict ordered the destruction of Christian scriptures and places of worship across the empire, and prohibited Christians from assembling for worship. Before the end of February, a fire destroyed part of the Imperial palace. Galerius convinced Diocletian that the culprits were Christians, conspirators who had plotted with the eunuchs of the palace. An investigation was commissioned, but no responsible party was found. Executions followed anyway, and the palace eunuchs Dorotheus and Gorgonius were executed. One individual, Peter Cubicularius, was stripped, raised high, and scourged. Salt and vinegar were poured in his wounds, and he was slowly boiled over an open flame. The executions continued until at least 24 April 303, when six individuals, including the bishopAnthimus, were decapitated. A second fire occurred sixteen days after the first. Galerius left the city for Rome, declaring Nicomedia unsafe. Diocletian would soon follow.
Although further persecutory edicts followed, compelling the arrest of the Christian clergy and universal acts of sacrifice, they were ultimately unsuccessful; most Christians escaped punishment, and pagans too were generally unsympathetic to the persecution. The martyrs' sufferings strengthened the resolve of their fellow Christians. Constantius and Maximian did not apply the later edicts, and left the Christians of the West unharmed. Galerius rescinded the edict in 311, announcing that the persecution had failed to bring Christians back to traditional religion. The temporary apostasy of some Christians, and the surrendering of scriptures, during the persecution played a major role in the subsequent Donatist controversy. Within twenty-five years of the persecution's inauguration, the Christian emperor Constantine would rule the empire alone. He would reverse the consequences of the edicts, and return all confiscated property to Christians. Under Constantine's rule, Christianity would become the empire's preferred religion. Diocletian was demonized by his Christian successors: Lactantius intimated that Diocletian's ascendancy heralded the apocalypse.[195]
Diocletian entered the city of Rome in the early winter of 303. On 20 November, he celebrated, with Maximian, the twentieth anniversary of his reign (vicennalia), the tenth anniversary of the Tetrarchy (decennalia), and a triumph for the war with Persia. Diocletian soon grew impatient with the city, as the Romans acted towards him with what Edward Gibbon, following Lactantius, calls "licentious familiarity".