Summary

Gaius Aurelius Valerius Diocletianus, born Diocles (Doclea or Salona, Dec. 22, 244), was a Roman emperor who ruled from Nov. 20, 284 to May 1, 305 under the imperial name Caesar Gaius Aurelius Valerius Diocletian Augustus Iovus (in the epigraphs GAIVS AVRELIVS VALERIVS DIOCLETIANVS AVGVSTVS).

Born into a family of humble origins in the Roman province of Dalmatia, Diocles (this was his original name) climbed the ranks of the Roman army until he became cavalry commander under Emperor Marcus Aurelius Carus (282-283). After the death of Caro and his son Numerian in the campaign against the Sasanians he was acclaimed emperor by the legions (on this occasion he changed his name to Diocletian) in opposition to Caro's eldest son, Marcus Aurelius Carinus, who had been appointed emperor by his father before the campaign and was in the West: the two clashed at the Battle of the Margus River, in which Carinus lost his power and his life (285).

With the advent of Diocletian came an end to the period known as the third-century crisis, characterized politically by a phase of internal turmoil (military anarchy), which lasted for almost fifty years and saw a large number of emperors succeed each other whose rise and stay in power depended solely on the will of the army. To put an end to this instability, which had become dangerous for the survival of the empire, he enacted a series of profound political and administrative reforms, among which the sharing of the empire among several colleagues stands out in the latter respect. The empire in fact became a tetrarchy.

To this end, in 285 he chose his fellow emperor Maximian as co-emperor, conferring on him precisely the title of Augustus and assigning to him the western half of the Empire (reserving the eastern half for himself). On March 1, 293, he completed the institutional architecture by associating the two Augusti with two Caesars (a sort of vice-emperors) in the persons of Galerius and Constantius, thus creating the so-called "tetrarchy," the "government of the four": each Augustus would rule over half the empire assisted by his own Caesar, to whom he would delegate the government of half his territory and who would succeed him (as a new Augustus) after twenty years of rule, in turn appointing a new Caesar.

He separated the civil and military administrations by strengthening both and reorganized the administrative subdivision of the state, increasing the number of provinces as a result of the splitting up of the existing ones, which had proved too extensive and were therefore judged to be difficult to manage. He directed to new administrative centers the cities of Nicomedia, Mediolanum, Sirmio and Trier, considering them because of their proximity to the turbulent frontiers of the empire, more suitable places from which to coordinate its defenses than the ancient capital Rome. He completed the evolution in an autocratic sense of the institutional figure of the emperor (a process of transformation that began more markedly under the Severans and persisted throughout the third century), which in the substantive aspect involved the transition from the phase of government known as "principate" to that of "dominion," among other things manifesting itself outwardly by the elevation of the emperor above the masses through the introduction of a highly elaborate court ceremonial. The use of an architectural policy characterized by the implementation of massive building works (typical of the Tetrarchic period) framed this autocratic evolution.

To make the borders more secure Diocletian undertook a series of victorious military campaigns against the Sarmatians and Carpi between 285 and 299 and against the Alemanni in 288. Internally he quelled a rebellion in Egypt on several occasions in 297 and 298. He also supported his own Caesar Galerius in the latter's campaigns against the Sasanians (culminating in 298 with the sack of the enemy capital, Ctesiphon), then negotiated directly with the Persians an advantageous and lasting peace.

The growth of the administrative apparatus resulting from the reorganization of the provinces, the increase in the army's numbers due to the constant state of war and the need to keep the borders secure, and finally the ambitious building program required a radical reform of the taxation system aimed at ensuring that the huge expenses entailed by the costly Diocletian policy were covered. Therefore from 297 onward (as attested by an inscription found in Egypt) taxation was fundamentally focused on payment per individual and per plot of land. However, not all of Diocletian's reforms had the hoped-for effects and some of them failed while the emperor was still in power such as the Edict on Maximum Prices (301), the purpose of which was to control inflation (due to currency devaluation) through the introduction of capped prices, which was instead counterproductive and quickly forgotten.

Moreover, immediately after his own abdication Diocletian had to watch helplessly the collapse of the tetrarchic system since the tetrarchy, which gave the impression of being a very efficient system of government as long as its originator remained in power, no less collapsed in the aftermath of his abdication as a result of the dynastic aims of Maxentius and Constantine, sons of Maximian and Constantius respectively. Finally, the anti-Christian religious policy pursued by Diocletian between 303 and 311 with a persecution that turned out to be the most violent ever enacted against Christians failed to eradicate Christianity, which indeed from 311 (the Edict of Serdica) gradually supplanted paganism until it became the official religion of the empire in 380 with the Edict of Thessalonica.

Despite these failures on the work of reform, a substantially positive judgment can be made of Diocletian because he succeeded, undoubtedly, if not in arresting at least in considerably slowing down the process of decay to which the Roman Empire had been subject since the death of Emperor Septimius Severus and which had undergone a dangerous acceleration during the third century. So that the 20-year Diocletian period propped up the Roman state by endowing it with the institutional, administrative, financial and military instruments (later perfected by Constantine) suitable to enable it to exist as a great power for at least most of the 4th century.

A Diocletian weakened by illness abdicated on May 1, 305, the first and only emperor to make this choice voluntarily. He retreated to his palace in Split on the Dalmatian coast until his death in the spring of 313, rejecting calls to resume power in the political chaos that corresponded with the collapse of the Tetrarchy.

Origins and military career

Neither the place nor the date of his birth is known with certainty about Diocletian. Certainly born in Dalmatia, he would have been named Diocles after his mother's name or the supposed native city of Doclea (or Dioclea), while his father would have been a freedman, scribe of the senator Anullinus. If it is conceded that he lived 68 years and died in 313, he should have been born in 243-244; but it has been suggested either that Diocletian died in 311 or 312, so that he would have been born in 242-243, or that Diocletian did not die at 68 but abdicated at that age, so that the year of his birth would be 236; and it has been held that December 22, the date of his acclamation as emperor, is also the day of his birth. As for the city of his birth, in addition to Doclea, Salona has been thought of, solely on the assumption that he decided to retire to Split, a suburb of Salona, out of a desire to live out his last years in his hometown.

His humble origins, which must not have allowed him a high-level education, are probably the reason for the lack of information about his early years. Before 270 he entered the army, in accordance with a tradition that saw Illyricum-the present-day Balkans-as a privileged region for recruiting the military and lower-ranking officers of the Roman legions: on the other hand, from the third century onward being a legionnaire meant, for one belonging to the rank of humiliores, joining the higher category of honestiores. With the reforms brought about by Gallienus, in fact, both the social composition of military commanders and their direct subordinates, formerly an aristocratic monopoly, and that of the intermediate officers, once the privilege of the equestrian order, had changed: after 260 the command of the legions and the office of military tribune was assigned to career officers often of low social origin. It was now possible, even for a simple legionnaire who distinguished himself by skill and discipline, to climb the various ranks in the army - centurion, protector, dux - up to prestigious administrative posts such as praefectus.

Regarding Diocletian's military career, the often unreliable Historia Augusta reports that he served in Gaul during the time of Aurelian but this information is not confirmed by other sources and ignored by modern historians. According to the historian John Zonara, around 280 Diocles would have been dux Moesiae, that is, commander of the army stationed in Mesia, a region corresponding to present-day Serbia, guarding the borders of the lower Danube. When Probus was overthrown and killed in 282 and the prefect of the praetorium Marcus Aurelius Carus proclaimed emperor, Diocles became domesticus regens, i.e., commander of the protectores domestici, the emperor's mounted guard, and the following year was appointed suffect consul.

Rise to power

In 283 Diocles took part in Caro's expedition against the Sasanids. The Romans gained an easy victory over the enemy, as the Sasanian ruler Bahram II was busy putting down a revolt led by his brother Ormisda and some Persian nobles who had risen against him, but Emperor Caro died suddenly (July

When the army stopped at Emesa, Numerian was apparently still alive and in good health (here, in fact, he promulgated his only surviving rescript), but when he left the city, his associates said he was suffering from an eye inflammation, and Numerian continued the journey in a closed chariot. On reaching the vicinity of Nicomedia, some soldiers smelled a foul odor coming from the chariot; they opened it, and found there the corpse of Numerian, who had been dead for several days.

The Roman generals and tribunes gathered to deliberate on the succession, and they chose Diocles as emperor. Diocles was proclaimed emperor by his fellow generals on a hill three miles from Nicomedia. Then, before the army acclaiming him augustus, the new emperor swore that he had had no part in the death of Numerian, and that Apro had killed the emperor and then attempted to conceal his death; Diocles then drew his sword and killed Apro; according to the Historia Augusta, he quoted a verse from Virgil as he did so. thus fulfilling the prophecy he had received when in about 270, while he was carefully counting the denarii to pay for the meal he had eaten at a tavern near Liege, a druidess approached him and scolded him for his miserliness; to which the man replied that when he became emperor he would spare no expense. Then the druidess warned him not to joke and prophesied that he would become emperor after killing a boar (aper, openers in Latin). Thus it was that Diocles by killing Apro became emperor.

This traditional narrative of events is not entirely accepted by historical critics: already Edward Gibbon argued that Apro was killed "without giving him time to enter into a dangerous justification," and Diocletian's own public protestation of innocence during the investiture ceremony appears suspicious and at least shows that Apro's guilt must not have been as obvious as it was later made to appear. It is possible that Diocletian was at the head of a conspiracy of the generals who got rid of both Numerian, a young man more devoted to poetry than to arms, Moreover, historically Diocletian did not intend to present himself as Numerian's avenger, so much so that he had his name erased from many official epigraphs, and by the panegyrist Claudius Mamertinus Diocletian was described as a liberator "from a most cruel domination."

Shortly after Apro's death, Diocles changed his name to the more Latinizing "Diocletian," adopting the name Gaius Aurelius Valerius Diocletian.

There remained to be resolved the division of power with Numerian's older brother, Carinus, who after his father's death had quickly made his way to Rome and assumed the consulship for the third time in 285. Carinus, having Numerian deified, declared Diocletian a usurper and with his army moved eastward; along the way, near Verona, he defeated in battle and then killed the governor Marcus Aurelius Sabinus Julianus, who had proclaimed himself emperor. Julian's revolt (and its tragic conclusion) provided Diocletian with the pretext to present Carinus as a cruel and oppressive tyrant.

Diocletian in turn assumed the consulship, and chose Caesonius Bassus as his colleague. Bassus came from the Campanian senatorial family of Caesonii, and had already been consul and proconsul of Africa three times, a distinction desired by the emperor Probus. He was thus a politician with the experience in government affairs that Diocletian presumably lacked. By his choice to assume the consulship (with a colleague from the ranks of the Senate) he intended to emphasize his opposition to the Carinus regime with respect to which he rejected any form of subordination, while also demonstrating his willingness to continue his collaboration with the senatorial and military aristocracy, whose support he needed to concretize his success both in the present (as he marched on Rome) and in the future to consolidate himself in power.

Over the winter 284

At the end of the battle, Diocletian, having received an oath of allegiance from both the victorious and the newly defeated legions, who acclaimed him Augustus, departed for Italy.

Having installed himself in power, Diocletian, convinced that the empire's existing system of government was now manifestly inadequate to administer a vastly extended territory whose frontiers were subject to the threatening and growing pressure of hostile peoples (as events, even recent ones, had amply demonstrated), resolved to create a new one. He instituted, therefore, a "quadricephalic" type of government structure, known as the tetrarchy, at the apex of which were placed two emperors (with the title Augustus) each at the head of the two territories into which the empire came to be divided: the West and the East. The two Augusti were assisted by two Caesars of their choice, who exercised almost direct control over half of the territory ruled by the respective Augustus they were destined to succeed, in turn choosing a new Caesar. The tetrarchic system formally came to an end in 324, when Constantine I, after defeating Licinius, ending a long civil war that had lasted since 306, reunified the Roman West and East in his own hands.

Introducing the new system of government, Diocletian gave himself the title Augustus of the East, establishing his capital at Nicomedia, and appointed Maximian Augustus of the West, who chose Mediolanum (Milan) as his capital. During the third century already other emperors, on more than one occasion, preferred to Rome (rendered by its geographical position too distant from the turbulent Rhine and Danubian frontiers), those cities (such as Milan) that would enable him to reach quickly the areas threatened from time to time. With Diocletian this fact was somewhat institutionalized. Rome nevertheless remained the ideal reference point of the Empire, remaining the seat of those institutions (such as the Senate) that had been reduced to a purely symbolic role following a centuries-long process of erosion of their original prerogatives. Effective power was now confined to the emperor and the circle of his closest associates (consilium and then consistorium), in the new administrative centers of the empire (Nicomedia and then Constantinople, in the pars Orientis). In 293, Diocletian appointed Galerius his Caesar, and Maximian did likewise with Constantius Chlorus. The territory of the Empire was divided into twelve dioceses that grouped several provinces (increased in number). As a result of this territorial and administrative reorganization, any residual privilege of Italy fell away, and it found itself completely equated with the other parts of the Empire. The various dioceses were in turn grouped into four larger regions, called prefectures, each governed by a person of imperial dignity (prefect of the praetorium).

Kingdom (284-305)

Diocletian may have been engaged in fighting the Quadi and Marcomanni immediately after the battle of the Margus River. It is certain that, after his victory over Carinus, he headed to northern Italy to initiate the establishment of a new government apparatus, but it is not known whether he descended as far as Rome on that occasion. There is a coinage issue suggesting an adventus of the emperor in the city, but some modern historians point out that Diocletian began his reign from the date of the army's acclamation and not from the date of ratification by the Roman Senate, following the example of Caro, who had called senatorial ratification an unnecessary formality. However, even in the event that Diocletian had gone to Rome in the aftermath of his own accession to power, he did not remain there for long, his presence in the Balkans being attested on November 2, 285, during a campaign against the Sarmatians.

Except for the replacement of the urban prefect of Rome with his own colleague in the consulate, Caesonius Bassus, it does not appear that Diocletian carried out a thorough purge of personalities involved with the previous regime. In fact, at least for the time being, most of the officials who had served under Carinus retained their posts, including Aristobulus whom Diocletian confirmed to the consulate and praetorian prefecture, despite the fact that he had betrayed Carinus (perhaps in common with many others retained in their posts), and later appointed proconsul of Africa and urban prefect: an act that historian Aurelius Victor described as an unusual example of imperial "clementia."

It had become clear from the events of the last decades how much the occurrence (sometimes simultaneously) of regional crises (Gaul, Syria, Egypt, lower Danube) placed, moreover, at a great distance from each other and in a very extensive territorial context, made it rather difficult (if not impossible) for a single emperor to remedy them. This was true even in cases where there were capable and energetic personalities at the head of the state, such as Aurelian and Probus, whose work was abruptly interrupted by the conspiracies of their own officers to which they fell victim. Considerations of this kind contributed to the maturation in Diocletian's mind of the conviction that the division of governmental responsibilities among several emperors was the most suitable remedy to "cure" the process of the Empire's decay. Therefore, in 285 in Mediolanum, barely a year after he ascended to power (and this might lead one to suppose that Diocletian already reached this conclusion several years before he became emperor), Diocletian chose Maximian as his colleague, conferring on him the title of caesar and thus making him to all intents and purposes a co-emperor. Maximian's loyalty to Diocletian was a determining factor in the initial successes of the diarchy (later Tetrarchy). The two emperors divided on a geographical basis the government of the empire and the responsibility for defending the borders and fighting usurpers, in their respective areas of responsibility.

The idea of shared sovereignty was certainly not new in the Roman Empire. Augustus, the first emperor, had shared power with his colleagues, and more official forms of co-emperorship existed from Marcus Aurelius (161-180) onward. More recently, Emperor Caro and his sons had ruled together, though without much accomplishment. And Diocletian was in an even more difficult situation than his predecessors in that he had a daughter, Valeria, but no son: his co-emperor would come from outside his family circle with all the risks in terms of reliability that this entailed. Some historians claim that Diocletian had adopted Maximian as filius Augusti upon his acclamation as emperor, following the example of some of his predecessors, although not all historians agree on this reconstruction.

The relationship between Diocletian and Maximian was quickly redefined in religious terms. In about 287 Diocletian assumed the title Iovius, Maximian that of Herculius. The title was probably meant to evoke certain characteristics of the ruler by whom it was used: Diocletian, associated with Jupiter, was reserved the main role of planning and commanding; Maximian, likened to Hercules, would have had the role of "heroically" carrying out his colleague's instructions. Despite these religious connotations, emperors were not "deities," in keeping with the characteristics of Roman imperial worship, although they could be hailed as such in imperial panegyrics; instead, they were seen as representatives of the deities, charged with executing their will on earth. True, Diocletian elevated his imperial dignity above the human level and Roman tradition. He wanted to result untouchable. He alone resulted dominus et deus, lord and god, so much so that all those around him were given, as if by reflex, a sacred dignity: the palace became sacrum palatium and his advisers sacrum consistorium. Obvious signs of this new monarchic-divine qualification were the emperor's court ceremonial, insignia and robes. He, in fact, instead of the usual purple, wore silk robes embroidered in gold, footwear embroidered in gold with precious stones. His throne then rose from the ground of the sacrum palatium of

The shift from military acclamation to divine sanctification aimed to deprive the army of the power to choose emperors and to influence the mechanisms of imperial succession; religious legitimation elevated Diocletian and Maximian above potential rivals with an effectiveness that neither military power nor dynastic claims could boast.

After being appointed caesar, Maximian was sent to fight the Bagaudians in Gaul. Diocletian, on the other hand, returned to the East and en route, reached the town of Citivas Iovia (Botivo, near Poetovio, now in Slovenia) on November 2. In the Balkans, during the autumn of 285, emissaries from a tribe of Sarmatians asked the Augustus for help in recovering their lost lands or, alternatively, for the granting of grazing rights within the territory of the Empire. Diocletian's refusal was followed by an armed confrontation from which the Sarmatians emerged defeated. But the Roman victory, crushing as it was, did not solve the problem of the growing pressure (and encroachments) of the nomadic tribes along the Empire's Danubian frontier: it would soon be necessary to confront them again.

In fact, not long afterward Diocletian was forced to repel new Germanic-Sarmatian invasions, not only in Pannonia but also in Moesia, fostered by the reduction of garrison contingents along the lower-middle Danubian frontiers to meet the troop requirements that the recently concluded civil war from time to time demanded of the various contenders. As a result of his reported successes over the Quadi and Iazigi he received the appellation "Germanicus maximus."

In the summer of that same year Maximian moved into Gaul, confronting the Bagaudian rebels. The accounts of this summer campaign that have reached us are not helpful in providing more details. In the fall two barbarian armies, one of Burgundians and Alemanni, the other of Chaibones and Eruli, forced their way through the Rhine limes and entered Gaul. While the first army was decimated by the hardships it suffered from starvation and disease, Maximian concentrated his efforts on the second, which he defeated as soon as it was intercepted, thus deciding to establish his headquarters on the Rhine in anticipation of future campaigns. For such success, Maximian was first given the appellation "Germanicus maximus," and Diocletian an iteration of this cognomen he had previously assumed.

In the winter of 285-286 Diocletian, who resided in Nicomedia, moved some settlers from the province of Asia to Thrace to repopulate the rural areas of this province following the flight of some of its inhabitants caused by a revolt. In the spring of 286 he visited the province of Syria-Palestine, although some sources would shift the date to the spring of 287. His presence in the region would also emerge from the Hebrew Midrash, according to which Diocletian, during the period in question, stayed in Panias (today Banias) on the northern Golan Heights. Diocletian took advantage of his proximity to the eastern frontier to intensify diplomatic contacts with the Sasanian Empire, aimed at initiating a phase of détente in relations between Rome and Persia. Successes in this regard were not long in coming: in 287, Bahram II sent precious gifts, a declaration of friendship between the two Empires, and an invitation addressed to Diocletian himself to visit him. However, from some Roman sources it appears instead that the Persian goodwill was not the result of diplomacy but simply a spontaneous initiative.

Also during the same period, perhaps in 287, the Sasanids, in confirmation of their desire for peace with Rome arising from the recent reopening of diplomatic channels between the two empires, renounced all claims on neighboring Armenia while also recognizing Rome's authority west and south of the Tigris River. In addition, the western part of Armenia was made a Roman province while Tiridates III, Arsacid, who had been claiming the Armenian throne ever since, being a client of Rome, he was forced to take refuge in the Roman capital following the Persian conquest of 252-253, was able, in 287, to return to claim the eastern part of his former domains without encountering any opposition from the Persian side. The gifts received by Bahram II, were interpreted as symbols of a Roman victory over the Sasanids (of which the resolution of the Armenian question was the substantial aspect), so much so that Diocletian was hailed as the "founder of eternal peace." These events may have represented the formal end of Caro's Sasanian campaign, which had probably ended without the conclusion of an actual peace treaty. At the conclusion of peace talks with the Persian-Sasanian, Diocletian undertook a reorganization of the Mesopotamian frontier in the course of which he fortified the city of Circesium (Buseira, Syria) located on the Euphrates.

While a compromise with the Persians was being peacefully reached in the East, in the West (in 286), the prefect of the English Channel Fleet, the future usurper Carausius, who had the city of Gesoriacum as the main headquarters of the fleet, successfully repelled attacks by Frankish and Saxon pirates along the coasts of Britain and Belgic Gaul, so much so that for such victories Diocletian assumed the title "Britannicus maximus." At the same time, Maximian defeated Burgundians and Alemanni, as reflected in one of his panegyrics dating from 289. But the internal stability of the western part of the Empire began to falter when Carausius preferred to appropriate the property confiscated from the pirates rather than allocate it to the state. Maximian then issued a death sentence against his treacherous subordinate, but Carausius preferred to flee Gaul, proclaiming himself Augustus and instigating revolt against Maximian and Diocletian in Britain and northwestern Gaul. Following this event, Diocletian himself decided to renounce the title "Britannicus maximus" assumed earlier, out of a sort of damnatio memoriae with respect to the victories achieved by Carausius before his usurpation.

On the basis of the surviving archaeological finds, it has been suggested that Carausius, at the time of the revolt, already controlled a number of military posts in Britain that guaranteed him a solid power base both in Britain and in northern Gaul: a coin found in Rouen attests that his power at the beginning of the revolt had extended as far as this continental area, due to the weakness of the central government. Carausius strove for legitimacy from Diocletian, as if he were a designated caesar: in his coinage (which had a far better quality than official coinage, particularly in his silver pieces) he extolled the "concord" between him and the central power (PAX AVGG "the peace of the three Augusti," we read on a bronze coin of 290, where we find on the obverse the image of Carausius along with that of Diocletian and Maximian, with the caption CARAVSIVS ET FRATRES SVI, "Carausius & his brothers"). However, Diocletian could not allow a usurper to join his imperial government, as had happened in the past to Postumus, just because he claimed it. In fact, his yielding to Carausius' demands would have set a dangerous precedent for the hold of the empire that Diocletian was preparing to reform, possibly opening the way for further usurpations: Carausius was, therefore, to be neutralized.

Prompted by the pressures of critical events, Diocletian resolved to elevate Maximian to the title of Augustus on April 1, 286, giving him, among other things, the appellation Nobilissimus et frater. However, a precise dating of this conferment cannot be established with absolute certainty. In fact, while some claim that Maximian received the investiture to Augustus from the beginning, without having previously held the office of Caesar, others believe that his elevation to the dignity of Augustus occurred on March 1, 286. But that of April 1, 286 remains the date on which most modern historians agree. The manner of Maximian's appointment presents unclear implications, it being rather doubtful that Diocletian was present at the event. It has even been suggested that Maximian had at first usurped the title and only later obtained its recognition by Diocletian, who was more concerned with averting the rekindling of new civil war than with having a colleague. This interpretation is largely in the minority because it lends itself to the criticism that, on the basis of multiple clues, it would appear quite clearly that Diocletian had from the outset determined that Maximian could act with a certain amount of independence. Finally, a part of modern historiography argues that Diocletian's choice may have been dictated by the need for the imperator

In the new system of power distribution that had come into being, Diocletian considered himself under the protection of Jupiter (Iovius) so as not to give rise to any doubts about the position of supremacy he intended to establish vis-à-vis his colleague Maximian, who in turn was associated "simply" with Hercules (Herculius, son of Jupiter). Such a system, conceived by an emperor coming from the ranks of the army such as Diocletian was, could only be extremely hierarchical.

The following year (287), Maximian, realizing that he was still unable to confront the usurper Carausius directly, preferred to strike him indirectly by devoting himself to fighting the Germanic tribes across the Rhine. Indeed, Maximian's military campaigns seem to have been aimed at undermining the authority of the separatist emperor of Britannia by depriving him of his support bases on the continent, Carausius having previously allied himself with the Franks. Thanks to Maximian's successes against the Alemanni and Burgundians on the upper Rhine, and against the Saxons and Franks along the lower reaches of the same river, Diocletian was renewed the appellation "Germanicus maximus" twice during the course of the year.

In the spring of 288, Maximian was preparing to assemble a large fleet to undertake an expedition against Carausius. Diocletian, in turn, returned from the East to meet with Maximian and agree with him on a joint campaign against the Alemanni, probably to secure the Rhine frontier in view of Maximian's impending campaign against Carausius. Based on the predetermined strategy, Germania Magna was invaded from two separate directions, Diocletian moving from Retia, while Maximian advanced from Mogontiacum (Mainz). Each emperor wrought destruction as he penetrated enemy territory, burning crops and livelihoods of the Germanic populations. These successes resulted in the annexation of new territories and allowed Maximian to continue his war preparations against Carausius without running the risk of aggression on his own right flank (the Rhine precisely) as soon as he initiated the attack. At the end of 288 dates Diocletian's fourth acclamation as "Germanicus maximus." Also that same year Maximian took the Frankish king Sali, Gennobaude, prisoner, obtaining in exchange for his release the return of all Roman prisoners in Frankish hands. To complete the work of pacification, he displaced some Franks in the territories surrounding Augusta Treverorum and Bagacum (present-day Bavay, Belgium).

Back in the East, Diocletian again found himself engaged in a further short campaign against the Sarmatians. No details of the military events have reached us, except for a few inscriptions from which we learn that Diocletian was first hailed with the victorious title of Sarmaticus Maximus (in 289). In the same period there is another success over the Alemanni of which the future Caesar, Constantius Chlorus, was the architect this time.

In the East, Diocletian attempted, by resorting to diplomacy, to reestablish relations with the nomadic desert tribes settled in the region close to the border with Persia, perhaps with the aim of reducing their incursions, or to restore Roman influence in the area to the levels reached at the time of the Palmyrene reign. If we bear in mind that some of these tribes had been clients of Persian kings, we can understand Diocletian's attention to them in order to strengthen the eastern limes, especially in light of recent tensions with the Sasanians. However, it is not clear from the information we have whether the emperor succeeded in his intent. In 290 dates the first historically established mention of the Arab tribe of Saracens (believed to have originated in the Sinai Peninsula), of whom the Romans crushed an attempted invasion of Syria.

In the West Maximian suffered the loss of the fleet recently fitted out to confront the usurper Carausius, but the precise date of the disaster is not certain, although it is presumably placed in the spring of 290. Latin panegyrics report that a storm was at the origin of the loss, but this may simply have been an attempt to conceal an embarrassing military defeat. As soon as he was informed of this, Diocletian interrupted his visit to the eastern provinces and quickly returned westward, reaching Emesa on May 10, 290, and Sirmium on the Danube on July 1, 290.

The meeting between Diocletian and Maximian, which took place in Mediolanum (Milan) in either late December 290 or January 291, was organized with a stage apparatus of solemn pomp and circumstance, marked by frequent public appearances by the two emperors. This has led to speculation that the ceremonies were organized to unquestionably confirm Diocletian's support for his troubled colleague. On that occasion, a delegation of senators from Rome joined the two Augusti, perhaps to demonstrate by their presence the survival of a certain prestige on the part of the capital of the Roman Empire, very often discarded as its own seat, by various emperors, over other cities. But it had long been customary for Rome to be used only as a "ceremonial" capital, while the administrative headquarters was determined, from time to time, by the needs of defending the imperial borders: already Gallienus (253 - 268), had chosen Mediolanum as his headquarters. If the panegyric, detailing the ceremony of the Mediolanum meeting, asserts that the real center of the Empire was not Rome, but where the emperor was ("the capital of the Empire seemed to be there, where the two emperors had met"), this simply echoes what the historian Herodian had anticipated in the early third century, that "Rome was where the emperor was." The political and military decisions that resulted from the Mediolanum summit were not made public. The Augusti had no further meetings until 303.

Some time after his return to the East, and before 293, Diocletian transferred command of the war against Carausius from Maximian to Flavius Constantius. A former governor of Dalmatia, a man of proven military experience dating back to the time of Aurelian's campaigns against Zenobia (272-273), Constantius, at the time of his appointment, held the position of prefect of the praetorium of Maximian in Gaul, whose daughter, Theodora, he had married. On March 1, 293, in Mediolanum (Milan), he was also awarded the title of caesar by Maximian. In the spring of 293, either at Philippopolis (Plovdiv, Bulgaria) or at Sirmium, Diocletian did the same with Galerius (perhaps already his praetorian prefect), to whom he had given his own daughter, Valeria, in marriage. Constantius was given Gaul and Britain; Galerius Syria, Palestine, Egypt, and responsibility for the eastern borders.

According to the new model of tetrarchy the Augustus of the East (Diocletian) would govern the provinces of Asia, Bithynia and Pontus, Galatia, Lycia and Pamphylia, Cilicia, Cappadocia, Cyprus, Syria, Judea, Arabia Petrea, Egypt, and Cyrenaica and Crete ; the Caesar of the East (Galerius) would rule the provinces of Cyrenaica and Crete , of Achaia, Epirus, Macedonia, Thrace, Upper Moesia, Lower Moesia, Dacia, Dalmatia, Lower Pannonia and Upper Pannonia; the Augustus of the West (Maximian) would rule Italy and the provinces of Africa, Mauretania Caesariensis, Sicily, Sardinia and Corsica, Cottian Alps, Noricum and Rhaetia; the Caesar of the West (Constantius Chlorus) would govern the provinces of Maritime Alps, Pennine Alps, Narbonense Gaul, Lugdunense Gaul, Aquitania Gaul, Belgic Gaul, Upper Germany, Lower Germany, Britain, Tarraconense Spain, Lusitanian Spain, Betica Spain, and Mauretania Tingitana.

This new arrangement of the state that had arisen as a result of the association of a caesar with each augustus is commonly referred to as tetrarchy, a term derived from ancient Greek and whose meaning consists of the "rule of the four." The tetrarchs was more or less sovereign in their territories; they traveled having a full-fledged imperial court (composed of administrators and secretaries, among others) as well as a personal army in their retinue. They strengthened the bond between them more by a shrewd policy of arranged marriages and blood ties: Diocletian and Maximian (the two Augusti) regarded each other spiritually as brothers and formally adopted Galerius and Constantius (already their sons-in-law) as their respective sons in 293. These relations implied a line of succession by virtue of which Galerius and Constantius would become Augusti after Diocletian and Maximian left office. The bond between the tetrarchs was further welded by marriage ties: Galerius married Diocletian's daughter Valeria, while Constantius married Maximian's stepdaughter Theodora; in turn, Maxentius, Maximian's eldest son, took Valeria Maximilla, Galerius' daughter, as his wife, while Constantine, Constantius' eldest son, was promised the hand of Fausta, Maximian's daughter, and was sent to Diocletian's court in Nicomedia to be introduced to the military and governing arts: according to a modern interpretation, corroborated by a passage from Lactantius, the d

The victory achieved by Constantius Chlorus in 293 over the Frankish allies of the rebel Carausius in the region between the Rhine and Scheldt estuaries procured Diocletian's fifth acclamation as "Germanicus maximus." Constantius' success constituted the conclusion of a series of military operations, which he had undertaken in Gaul even before he became Caesar, aimed at depriving Carausius of his support bases on the continent and which had in the bloody expulsion of Boulogne, at the end of a long siege, one of the crucial steps. The loss of Gaul brought about the fall of Carausius, who was assassinated and replaced by one of his collaborators, Alletto. The latter became the animator of Britain's resistance for another three years, until the island was subjected to an invasion that within a short time suppressed the separatist rebellion. The main perpetrators of the revolt were put to death after being finally defeated, near present-day Farnham, by Constantius' prefect of praetorium, Julius Asclepiodotus, while Alletto was killed in the heat of battle. Constantius himself, after landing in the southeast of the island, entered Londinium (London), previously sacked by Alletus' Frankish deserters, where he was welcomed as a liberator. For that event a series of gold medallions were minted in Trier, commemorating Constantius on the reverse side as Redditor Lucis Aeternae ("restorer of eternal light"), associat

Between 293 and 294, Galerius, soon after his appointment as Caesar, undertook to suppress a local revolt in Upper Egypt. Two years later (295) he moved to Syria to counter a new threat from the Sasanian Empire. Meanwhile, deep discontent began to spread in Egypt, caused by Diocletian's decision to equalize the level of taxation with that of the other Roman provinces, which later degenerated into a full-fledged popular uprising that broke out soon after Galerius' departure. At the head of the unrest was Domitius Domitian, who, proclaiming himself augustus in July

Diocletian took advantage of his presence in Egypt to reform the province's bureaucracy and to order a population census, depriving Alexandria, guilty of joining the revolt, of the ability to mint coinage on that occasion. The bureaucratic reforms implemented by Diocletian, combining with those made by Septimius Severus, streamlined Egyptian administrative procedures to the point of assimilating them to those of the other provinces of the Empire. During his Egyptian sojourn Diocletian traveled up the course of the Nile in the summer of 298, visiting Oxyrhynchus and Elephantine. In Nubia, he entered into a peace treaty with the Nobati and Blemmi peoples, under which the latter, in return for an annual gift of gold, made it possible to move the frontier as far as File. In the fall of 298, Diocletian left Egypt, heading for Syria (where he arrived in February 299), meeting, then, with Galerius in Mesopotamia.

With the suppression of the British separatist revolt, the most serious threat, up to that point, to the legitimacy of the Tetrarchs vanished, and this allowed Maximian and Constantius to concentrate their efforts on countering external threats. So that by 297 Constantius again returned to the Rhine to confront the Frankish pirates and the Alemanni, while Maximian embarked on a large-scale military campaign, first along the Danube and then in Africa, against the nomadic peoples, probably entering Carthage triumphantly on March 10, 298.

In 297, having finished the reorganization of Britain in consultation with his own Augustus Maximianus, Constantius Chlorus initiated the repopulation of the territory formerly inhabited by the Batavians with Salian Franks from Friesland. The following year (298), again the Caesar Constantius, who had been entrusted with the Rhine frontier, inflicted a heavy defeat on a coalition of Alemannic tribes in two major battles (Battle of Lingones and Battle of Vindonissa), which ensured the strengthening of this stretch of border for at least a few decades.

For these victories by Constantius, the tetrarchs pinned on themselves an iteration of the title "Germanicus maximus," the fifth for Diocletian, while in the year 302 a second battle seems to have taken place near Vindonissa, from which, again, Alemanni and Burgundians emerged defeated, but in all likelihood this should be the same battle as in 298.

Along the African limes, sources report a revolt that broke out in 293 among the Quinquegentians, which was tamed only four years later by Maximian. The latter, in fact, set out for Mauretania in late 297 (with a heterogeneous army consisting of contingents from the Praetorian Guard, legionaries from Aquileia, Egyptians and Danubians, Gaulish and German auxiliaries, and recruits from Thrace), and eradicated those of the Quinquegentians, who had also penetrated Numidia. Also in 297 Maximian began a bloody offensive against the Berbers that went on for a long time. Not content with driving them back to their homelands in the Atlas Mountains, from where they could have continued their raids, Maximian ventured deep into enemy territory inflicting as much devastation on them as possible for punitive purposes, driving them back as far as the Sahara. The following year (298) he reinforced the defenses of the African frontier from the Mauritanias to the province of Africa.

Diocletian spent the spring of 293 moving with his own caesar Galerius from Sirmium (Sremska Mitrovica, Serbia) to Byzantium (Istanbul, Turkey). Then, in October of that year, he returned to Sirmium, where, between the following winter and spring, he immersed himself in the preparations for a new military campaign against the Iazigi Sarmatians, which he personally led from the spring of 294 until (perhaps) the fall of that year, reporting a victory. Roman success procured for the empire the maintenance of calm along the Danubian section of the frontier, while it earned Diclezian the third acclamation as "Sarmaticus maximus." Further successes over the barbarian populations, this time of the Goths, would be placed in the same period, so that the tetrarchs assumed the title "Gothicus maximus."

To consolidate the strong position he had achieved on the Danube thanks to his recent military successes, Diocletian began the construction of a series of forts north of the river at Aquincum (Budapest, Hungary), Bononia (Vidin, Bulgaria), Ulcisia Vetera, Castra Florentium, Intercisa (Dunaújváros, Hungary), and at Onagrinum (Begeč, Serbia). These new fortifications were intended to be part of a new defensive line called Ripa sarmatica.

In 295 and the summer of 296 Diocletian again unleashed an offensive in the Danubian region, which ended with the defeat of the Carpi people and their partial transfer to Roman territory, in imitation of what Aurelian had already implemented with other defeated barbarian populations.

Later in 299, Diocletian and Galerius, once their operations in the East were over, returned to the Danubian border of Lower Moesia to oppose the Carpi, Bastarni and Sarmatians (or presumably Roxolans). On that occasion, too, the captives were transferred to Roman territory, forcing them to settle there (in Pannonia north of the Drava River, as alleged by Ammianus Marcellinus). The recent defeat inflicted on the Sarmatian tribes was worth procuring for Diocletian the fourth acclamation as "Sarmaticus maximus."

In 302, following Diocletian's forced return to the East, the direction of operations on the Danube passed to Galerius, who successfully completed the task entrusted to him. By the time of his abdication (305), Diocletian had succeeded in securing the frontiers along the entire length of the Danube, endowing them with a new and articulated defensive system characterized by new fortresses, bridgeheads, wide roads, and walled cities, and reinforcing the garrisons by sending fifteen or more legions to patrol the region. Confirming this, an inscription found at Sexaginta Prista on the lower Danube extolled the restored tranquilitas of the region. This policy of strengthening the borders involved enormous and costly efforts, but the costs incurred were more than compensated for by the benefits achieved in terms of defense and security when one considers the neuralgic importance of the Danubian region.

In 294, Narsete, son of Sapore I, seized the throne of Persia after eliminating Bahram III, who had ruled the Sasanian Empire since the death of Bahram II in 293. In early 294, Narses sent a series of gifts to Diocletian, following a long-established custom, which was followed by an exchange of ambassadorships between the two Empires. In Persia, at the same time, Narses arranged to erase all traces of his predecessor from public monuments, in a sort of damnatio memoriae. He wished to emulate the military exploits of the warrior kings who had preceded him, such as Ardashir I (226-241) and especially Shapur I (241-272), who had gone so far as to sack Antioch of Syria by taking the Roman emperor, Valerian (253-60), prisoner and adorning the walls of Persian temples with the remains of defeated enemies.

With such a frame of mind it proved inevitable that Narsees would declare war on Rome, in 295 or perhaps 296. The first Roman territory to bear the brunt of the aggressive Persian policy, being invaded, was the western part of Armenia, Rome's client kingdom, recently entrusted by the Romans to Tiridates after the peace of 287. The Sasanian king then directed his army southward, penetrating into the Roman province of Mesopotamia (in 297), where, in the region between Carrhae (Harran, Turkey) and Callinicum (Al-Raqqa, Syria), which historian Fergus Millar probably identifies along the Balikh River, he inflicted a heavy defeat on Galerius, who had come up against him, without waiting for the reinforcements that Diocletian was bringing him. Diocletian may have been present in the final stages of the battle, limiting the extent of the reversal, but he shifted the responsibility for the military failure onto his own caesar, as was clear from the official version that emerged at a public ceremony held in Antioch of Syria. Moreover, the Augustus publicly humiliated his Caesar, forcing him to walk in sumptuous clothes for a mile at the head of the imperial procession. However, it is possible that Diocletian's gesture toward Galerius was not dictated by an intention to inflict humiliation, but was simply part of normal court protocol.

Galerius asked and obtained from Diocletian a second chance to raise his own prestige and that of Roman arms. So that, in the second half of 297, his army was reinforced by a series of military contingents drawn from various legions (vexillationes), deployed along the Danubian limes. Narses, after his recent successes, had placed himself on the defensive, preferring to wait for the Roman counteroffensive, which, in implementation of the plans drawn up by the Romans, included an attack from Armenia in the direction of northern Mesopotamia. According to the account of Faustus of Byzantium, a battle was to take place after Galerius arranged at Satala (Sadak, Turkey) in Armenia Minor, his headquarters, and Narses advanced from his base at Oskha to attack him, although other sources of the period do not confirm these details. It is also unclear whether Diocletian was present at his caesar's military campaign or was rather in Egypt or Syria. Lactantius criticizes Diocletian for his absence from the front, but Southern, who dates Diocletian's Egyptian campaign a year before Barnes, places Diocletian in the rear, supporting Galerius along the southern front. What is certain is that Narses was forced to fall back to Armenia suffering, at a distinct disadvantage, from Galerius' initiative. The particularly rugged Armenian terrain lent itself more to the maneuvers of the Roman legionary infantry than to those of the Sasanian cavalry. These concomitant factors favored the success of Galerius, who prevailed over his Persian opponent in two successive battles. In the course of the second clash, Roman forces conquered Narses' camp, seizing his treasures, his harem, and taking the Persian king's wife prisoner. Galerius took advantage of the victory by continuing his advance along the lower reaches of the Tigris, eventually occupying the Persian capital Ctesiphon itself, before returning to Roman territory by moving up the course of the Euphrates River.

Rather than continuing military operations, taking full advantage of the gains made as a result of Galerius' victories, Diocletian preferred to take advantage of the position of strength held by Rome at the time to engage in peace negotiations with the enemy. After a disappointing start, marked by Galerius' rejection of ambassadors sent to him by Narses with a demand for the return of the family taken prisoner by the Romans, the actual peace negotiations began in the spring of 299. The magister memoriae (secretary) of Diocletian and Galerius, Sicorius Probus, was sent by the Sasanian king to explain the terms of the agreement desired by Rome. The terms of the so-called peace of Nisibis were weighty: Armenia was to return under Roman rule including the fort of Ziatha, located along the border; Caucasian Iberia was to be placed under the control of a Roman appointee; Nisibis, now in Roman hands, was chosen as the only city in charge of trade between the two empires; Rome would, in addition, exercise control over five satrapies between the Tigris and Armenia: Ingilene, Sophene, Arzanene (Aghdznik), Corduene (Carduene), and Zabdicene (near modern Hakkâri, Turkey). These regions included the stretch of the Tigris River that crossed the Anti-Taurus range; Rome would extend control over the Bitlis Pass, (located along the shortest route through Persian Armenia), and access to the region of T

Also dating from this period was the construction of a new line of fortifications: the strata Diocletiana. This was a via militaris, along the so-called stretch of limes arabicus, and thus including forts, blockhouses and watchtowers, and which remained in use until the 6th century. The road was equipped with a long series of fortifications, all built uniformly: these were rectangular castra with very thick walls and towers projecting outward. They were normally located within a day's march (ca. 20 Roman miles) of each other. The route began near the Euphrates at Sura, along the border facing the Sasanian Empire, and continued southwest, passing first through Palmyra and then Damascus and joining, then, with the Via Traiana Nova. Finally, a branch line should be noted that went east of the Hauran, through Imtan, to the oasis of Qasr Azraq. This was, in essence, a continuous system of fortifications connecting the Euphrates to the Red Sea near Aila.

After the conclusion of the Peace of Nisibis, Diocletian and Galerius returned to Antioch of Syria. During that year (in 299), the emperors took part in a religious ceremony culminating in a sacrifice for divinatory purposes. But the haruspices were unable to read the entrails of the sacrificed animals and accused the Christians present within the imperial court of this. The emperors therefore ordered that all members of the court perform a purifying sacrifice, later extending the request to the entire army, stipulating expulsion from the ranks for those who refused. Diocletian was a conservative in religious matters, respecting the traditional values of Roman religion including the rite of religious purification. However, Eusebius, Lactantius, and Constantine believed that it was Galerius (driven by political aims) who instigated Diocletian to rage against Christians. Thus there was a reversal of the policy of tolerance previously pursued by the imperial government.

Antioch was Diocletian's principal residence from 299 to 302, while Galerius preferred to avail himself of various locations (sometimes in concert with his Augustus) located along the lower-middle Danube frontier. Diocletian visited Egypt again in the winter of 301-302, granting a grain subsidy to Alexandria on that occasion. As a result of irreconcilable disagreements with the Manichaeans, which had arisen particularly in the course of public controversies, the Augustus ordered that the leaders of Mani's followers be thrown at the stake along with their sacred texts, initiating a full-fledged religious repression. On March 31, 302, as recorded in a rescript from Alexandria, he declared that Manicheans of low social rank were to be put to death, while those of high rank were to be sentenced to hard labor in the mines of Proconneso (in the Sea of Marmara, in present-day Turkey) or in those of Phaeno in southern Palestine. All Manichean property was confiscated and forfeited into the imperial treasury. Diocletian's aversion to Manichaeism was grounded in the peculiarities of this new creed: its novelty, its foreign origins, the way it corrupted the morals of the Roman race, and its opposition to pre-existing religious traditions. At the same time, Manichaeism was instead widely spread and tolerated in the Persian Empire, providing an additional foothold to aggravate the already strained relations between Rome and Persia, as Diocletian

Diocletian returned to Antioch in the fall of 302. The following year he took a first step in the repression of Christianity by having imprisoned and then executed (Nov. 17, 303) after horrendous tortures, the Roman deacon of Caesarea, who was found guilty of questioning the legitimacy to judge of the imperial courts and, above all, for refusing to perform, in deference to the emperor's instructions, ritual sacrifices to the gods. Thereafter, the Augustus moved to Nicomedia, accompanied by Galerius, where he spent the winter. According to Lactantius, the two emperors during their stay in Nicomedia planned the policy to be adopted toward the Christians. Diocletian initially intended to limit himself to banning Christians from administrative and military positions, believing such measures to be sufficient to appease the gods, but Galerius persuaded the Augustus to conduct a more decisive action that included the possibility of exterminating the adherents of this new religion. The arguments put forward by Galerius (during, it seems, secret meetings) in support of adopting the hard line toward the Christians could be summarized as follows: the Christians had created a state within the state, which was already governed by its own laws and magistrates, possessed a treasury, and maintained cohesion through the tireless work of the bishops who directed the various communities of the faithful to which they were in charge through decrees that were blindly obeyed; it was necessary, therefore, to intervene before Christianity irreparably "contaminated" the ranks of the army. According to sources of the time, the Didymaion, Apollo's oracle of Didima, was consulted before action was taken, but the response was that, "because of the ungodly on Earth, Apollo would not be able to provide help." The "ungodly" referred to by the oracle were identified (by much of the imperial court) with Christians, and Diocletian allowed himself to agree with this interpretation, probably delighted to have even a "religious" justification for unleashing a truly universal persecution.

The persecution began on February 23, 303, and was carried out with great ferocity, especially in the East, where the Christian religion was now remarkably widespread. The first edict was posted in the capital, Nicomedia,

In the space of a few days, before the end of February, twice Diocletian's palace and rooms suffered a fire. The strange coincidence was considered proof of the maliciousness of the two events, and suspicion, engulfed by Galerius, naturally fell on the Christians. An investigation was then promoted, but it yielded negative results, for no one responsible was found. Diocletian, then, feeling personally threatened, abandoned all residual caution and stiffened the persecution. Despite numerous arrests, tortures and executions everywhere, both in the palace and in the city, no confession of responsibility for the plot could be extracted. To some, however, Galerius' hasty departure from the city appeared suspicious, which was justified with the fear of falling victim to the hatred of the Christians. The court eunuchs, Dorotheus and Gorgonius, were initially put to death. The cubicular, Peter, was stripped, raised and scourged. Salt and vinegar were poured over his wounds, and he was slowly put on the fire and boiled to death. The executions continued until at least April 24, 303, when six people, including Bishop Antimus of Nicomedia, were beheaded. After the second fire, which broke out sixteen days after the first, Galerius abandoned the city for Rome, declaring Nicomedia unsafe, and shortly afterward Diocletian followed him as well.

Perhaps because of Diocletian's initial lack of animosity toward the persecution, who perhaps wanted to check its outcomes personally before having to intervene on a large scale, strangely the edict took almost two months to arrive in Syria and four to be made public in Africa. In the various parts of the empire, magistrates and governors nevertheless enforced the decree with varying severity (and sometimes with mildness), but the casualties and destruction of churches were numerous, as were the burnings of holy books (which, however, thwarted the work of the fire thanks to their spread). This edict was followed by others in which increasingly severe penalties were imposed, first on public officials, and then on all citizens of the Christian faith. Despite the increasing persecution, these proved fruitless. Most Christians managed to escape, and the persecution did not have the support of the pagans. The sufferings of the martyrs strengthened the resolve of their Christian brethren.

Eusebius would call the years that followed a real war: many were the lapsi, but also the martyrs. The greatest number of casualties occurred in the area controlled by Diocletian (in the less Christianized Balkans, the Caesar Galerius, often referred to as the inspirer of the persecution, was equally harsh. Also in Italy and West Africa, ruled by the Augustus Maximian, the violence was harsh and many martyrs were counted, although the fourth edict was applied in a limited way; in contrast, in Britain and Gaul the Caesar Constantius Chlorus, father of Constantine I, applied only the first edict. Epigraphic records and hagiographies believed to be authentic have come to commemorate the martyrs of this period.

The persecution took shape at a time when Christianity was well established in the empire (it is estimated that at the beginning of Diocletian's reign about 10 percent of the empire's population was Christian); however, there was no shortage of resistance: around 300 numerous anti-Christian publications circulated, ranging from the philosophical to the trivial. Diocletian's own wife and daughter were Christians. Diocletian was generally tolerant of political opponents, but he was very rigid against what he considered intellectual deviations: in 297, for example, he turned against the Manicheans. The difficult balance with Christianity held until 303. Several reasons have been proposed to explain the start of the persecution: reinforcement of prejudice, economic interests, reaction to the Christianization of Armenia.

At Diocletian's abdication in 305, the persecution had not achieved the desired results, yet hostilities against Christians nevertheless found continuation in the East under the governments of Galerius and Maximinus Daia, albeit intermittently, until 311. During the persecution, Christians also found protection in many places from neighboring pagans, a sign of growing popular tolerance of the new religion. The temporary apostasy of some Christians, and the surrender of scriptures, during the persecution played an important role in the subsequent Donatist controversy. Within the twenty-five years after the persecutions began, the Christian emperor Constantine, would rule the empire alone. He would make good the consequences of the edicts by returning all property previously confiscated from the Christians. Under his reign, Christianity would become the preferred official religion. Diocletian was demonized by his Christian successors: Lactantius hinted that his rise was the prelude to the apocalypse, and in Serbian mythology, Diocletian is remembered as the adversary of God.

Diocletian saw his task as that of a restorer, an authority whose duty was to restore the empire to peace, to restore stability and justice where the barbarian hordes had brought devastation. He took responsibility for regimenting, centralizing political authority on a massive scale. He imposed a value system toward the often different and unreceptive public from the provincials. In imperial propaganda of the period, recent history downplayed and distorted the significance of the tetrarchs as "restorers." Aurelian's successes were ignored; the revolt of Carausius was backdated to the reign of Gallienus, making it implicit that the tetrarchs' project produced Aurelian's defeat of the Palmyraeans; the period between Gallienus and Diocletian was effectively erased. The history of the Roman empire before the tetrarchy was interpreted as a period of civil wars, savage despotism and imperial collapse. In those inscriptions that bore their names, Diocletian and the other tetrarchs were referred to as "restorers of the whole world," men who succeeded in "defeating the nations of the barbarians, giving tranquility to their worlds." Diocletian was referred to as the "founder of eternal peace." The restoration theme was conjoined with an emphasis on the uniqueness and genius of the tetrarchs themselves.

The cities most widely used as imperial seats in this period were Mediolanum (Milan), Augusta Treverorum (Treveri), Arelate (Arles), Sirmium (Sremska Mitrovica), Thessalonica (Thessaloniki), Serdica (Sofia), Nicomedia (İzmit) and Antioch (Antakya). They were considered alternative imperial seats to the exclusion of the city of Rome and the senatorial aristocracy. The process of exauthorizing the Roman Senate as a decision-making authority was thus perfected: the empire became an absolute monarchy and took on characteristics typical of Eastern monarchies, such as the divine origin of the monarch and his worship.

A new ceremonial style was developed that emphasized and exalted the sacred figure of the emperor in relation to other people. The quasi-republican ideals of Augustus, primus inter pares, in which divine honor was rendered to the genius of the incumbent emperor (by burning incense in front of the statue) but deification was allowed only after death, were abandoned completely by all the tetrarchs. Diocletian began wearing a gold crown and jewels, prohibited the wearing of purple robes by all except emperors. Subjects were required to prostrate themselves in his presence (the more fortunate were granted the privilege of kissing the hem of his robe (a form of the religious rite called proskýnesis, προσκύνησις, which subjects of eastern rulers had used for centuries). Circuses and basilicas were built to highlight the grandeur, power, and authority of each tetrarch in their imperial seat. The figure of the emperor had a transcendent authority, a man above the masses. His appearance was managed in every detail. This style of presentation was not new; many of its elements had already been showing up during the reigns of Aurelian and Septimius Severus, who called himself dominus ac deus (before that with Caligula and Domitian, whose claim to be deus or deity already in life, and to cloak himself in oriental-type royal character was considered offensive by the Roman mentality of the time, however, and one of the causes of their assassination), but it was only under the tetrarchs that this was made so explicit.

The tetrarchy was planned first on a territorial basis, both because of the growing difficulties due to the many internal revolts within the empire and because of the devastating incursions of the barbarians along the outer borders. Provision was made to divide the empire into four parts, between two Augusti and two Caesars. Each of its parts then consisted of three dioceses, making a total of twelve.

The diocese was governed by a vicar praetor or simply vicar (vicarius), subject to the prefect of praetorium (some dioceses, however, could be governed directly by the prefect of praetorium). The vicar supervised the governors of the provinces (variously called: proconsules, consulares, correctores, praesides) and tried on appeal cases already decided in the first instance by them (the parties could choose whether to appeal to the vicar or to the prefect of praetorium). The vicars had no military powers; in fact, the troops stationed in the diocese were under the command of a comes rei militaris, who depended directly on the magister militum and had in his charge the duces who were entrusted with military command in the individual provinces. Below is the first reorganization desired by Diocletian with the tetrarchy, divided into 12 dioceses, 6 of which were in the West and 6 in the East.

To avoid the possibility of local usurpations, to facilitate more efficient collection of taxes and supplies, and to facilitate law enforcement, Diocletian doubled the number of provinces from fifty to at least one hundred.

Some of the provincial divisions required subsequent revisions, leading to changes soon after 293 or in the early fourth century. Rome itself (including its environs for a perimeter of about 150 km) was excluded from the authority of the praetorian prefect, as it was administered by an urban prefect of the senatorial order (the only prestigious official reserved exclusively for senators, with the exception of a few governors: in Italy with the title of corrector, as well as the proconsules of Asia and Africa.

This territorial division inevitably led to a growing number of imperial seats, alternatives to Rome:

The system proved effective for the stability of the empire and made it possible for the augusts to celebrate vicennalia, or 20-year reigns, as had not happened since the time of Antoninus Pius. The whole territory was redrawn administratively, abolishing the Augustan regions with their division into "imperial" and "senatorial." Twelve administrative districts (the "dioceses," three for each of the tetrarchs) were created, governed by vicarii and in turn divided into 101 provinces. It remained to test the mechanism of succession.

In keeping with made the transition from a republican to an autocratic ideology, Diocletian's court of councilors, his consilium, was different from that of previous emperors. He completely changed the Augustan illusion of an imperial government, born of cooperation between the emperor, the army and the senate. In his palace he established a structure that was to all intents and purposes autocratic, a change later summarized in the name consistory (consistorium), not a council. The term consistorium had already been used to define the place where these meetings of the imperial council took place. Diocletian regulated his court by beginning to distinguish it by separate departments (scrina) to which particular tasks were entrusted. From this structure were created the functions of the various magistri, such as the Magister officiorum, and associated secretariats. These were men in charge of dealing with petitions, requests, correspondence, legal affairs, as well as foreign embassies. Within his court, Diocletian maintained a permanent body of legal advisers, men with considerable influence on the reordering of legal affairs. Then there were two "ministers" of finance, who had to deal with both the public treasury (aerarium populi Romani) and the emperor's private domains (fiscus Caesaris), as well as the prefect of the praetorium, surely the most influential official of all. The reduction of the praetorian guard to the level of a mere garrison of the city of Rome greatly reduced military power in the hands of the prefect (although prefects such as Julius Asclepiodotus, who defeated Alletus in Roman Britain, were valiant military commanders), to the benefit of predominantly civilian duties. The prefect maintained a staff of hundreds and directed affairs in numerous disciplines of imperial government: from taxation, to administration, to legal matters, to minor military commands, so much so that the prefect of the praetorium often turned out to be second only to the emperor himself.

Overall, Diocletian generated a sharp increase in the number of bureaucrats within the imperial administration; Lactantius used to claim that there were more men using tax money than there were paying it. Historian Warren Treadgold believes that under Diocletian the number of people devoted to imperial administration doubled from 15,000 to 30000. Roger Bagnall estimated that there was one imperial official for every 5-10000 people in Egypt, that is, between 400 and 800 officials per 4 million inhabitants (Strabo, 300 years earlier, put it at 7.5 million, excluding Alexandria). And comparing Diocletian's Empire to the 5th-century Chinese Empire of the Song Dynasty, here there was one official per 15000 inhabitants. Jones estimated 30000 officials for an empire of 50-65 million, or one official for every 1,667-2,167 inhabitants, as the average for the entire empire. The number of officials and the percentage per inhabitant, naturally varied depending on the diocese, the number of provinces that made up the diocese and the population of those provinces. The provincial and diocesan staff was around 13 to 15,000, as established by law. The remaining 50% were with the emperor within his comitatus, along with various praetorian prefects, grain procurement officers (later for both capitals, Rome and Constantinople), from Alexandria, Carthage, as well as officials from the central offices of all provinces.

The spread of imperial law to the provinces was facilitated by the reform that Diocletian made at the level of provincial structure, now that there were more governors (praesides) making decisions over smaller geographic areas and smaller populations. Diocletian's reform made it one of the functions of governors to officially preside over the minor courts: whereas military and judicial functions in the high Roman empire were the typical functions of the governor, and procurators were in charge of taxation, under the new vicarii system, governors were responsible for justice and taxation, while a new type of official, the dux, acted independent of civil service, and held military command. These duces often administered the military forces of two or three of the new provinces created by Diocletian, commanding over military forces that could consist of 2,000 up to more than 20,000 armed men. In addition to their role as judges and tax-collecting officials, the governors had to maintain the postal service (cursus publicus) and ensure that city councils did their duty.

This reduction in the powers of the governors, as representatives of the emperors, may have reduced the political risks of an all-too-powerful class of imperial delegates, but it also limited the ability of the governors in opposition to local landowners, especially those of the senatorial order, who, though with fewer opportunities to obtain a given office, retained wealth, social prestige, and client relationships (especially in relatively quiet regions where a strong military presence was not necessary). On one occasion Diocletian had to urge a proconsul of Africa, to on fear the consequences of large landowners of senatorial rank. If a governor of senatorial rank was subjected to such pressures, we can imagine what difficulties simple praeses faced. This explains the difficult relationship between central power and local castes: in 303, an attempted military sedition Seleucia of Pieria and Antioch of Syria forced Diocletian to exact tremendous revenge on both cities by putting to death several members of the city council for failing in their duty to maintain order in their jurisdiction.

Like most emperors, much of the daily routine revolved around legal affairs, responding to appeals and petitions, issuing judgments on controversial issues. Rescripts, authoritative interpretations issued by the emperor in response to a range of legal issues posed both between litigants in the public and private domains, were a common duty peculiar to second- and third-century emperors. Diocletian was inundated with such work, and he was incapable of delegating his duties. It would have been seen as a dereliction of duty to ignore them. In the itinerant imperial court of late antiquity, we can analyze the progress of the imperial retinue through the positions from which certain rescripts were issued-the presence of the emperor was what allowed the system to function. When ever the imperial court decided to settle in one of the capitals, there was an excess of petitions, as happened in 294 in Nicomedia, where Diocletian set up his winter quarters.

Certainly the prefects of the praetorium (Aphranius Hannibalianus, Julius Asclepiodotus, and Aurelius Hermogenianus) helped regulate the flow and presentation of such documents, the deep sense of legality inherent in Roman culture meant that the workload was heavy. The emperors who had preceded Diocletian in the forty years prior to his reign had failed to meet their duties effectively, and their production of attested rescripts is low. Diocletian, on the contrary, was prodigious in his dealings: there are at least 1,200 rescripts in his name that still survive, and these represent only a small part of the enormous amount of work he did. The sharp increase in the number of edicts and rescripts produced under Diocletian's rule has been read as tangible evidence of a continuing effort to realign the entire empire to the conditions dictated by the central imperial power.

Under the leadership of jurists such as Gregory, Aurelius Arcadius Carisius, and Hermogenianus, the imperial government began publishing official books on legislative precedents, collecting and listing all the rescripts that had been issued from the principate of Hadrian (reign 117-138) to that of Diocletian. Codex Gregorianus included rescripts up to 292, which Codex Hermogenianus updated with a large collection of rescripts issued by Diocletian in 293 and 294. Although the act of codification itself was a radical innovation, which had the design of building on the precedents of the Roman legal system, the jurists generally remained conservative, observing the practice and theory of the ancient Roman past as their guide. They probably gave more free rein in the compilation of the codices than did later compilers of Codex Theodosianus (438) and Codex Iustinianus (529). The Gregorian and Hermogenian codices were not yet subject to the iron structure of the later codices, and they were not published under the name of their emperor (Codex Diocletianus), but under the name of their compilers. Their official characteristics were clear. They were collections, later recognized in the courts as authoritative sources of imperial legislation up to the date of their publication and regularly updated.

After Diocletian's reform of the provinces, governors were called iudex or judge. The governor became responsible for his decisions, first to his superior as well as to those of the emperor. It was around this time that judicial documents became transcripts of what was said in the course of the trial, making it easier to determine bias or improper behavior on the part of the governor. With these sources and the universal right of appeal, imperial authorities probably had great power to enforce standards of behavior by their judges. Despite Diocletian's reformist attempts, provincial restructuring was far from clear, especially when citizens appealed against the decisions of imperial officials. Proconsuls, for example, were often judges of first instance and the next appellate level, and governors of some provinces received appeal cases from neighboring provinces. Soon it became impossible for the emperor to avoid dealing with some arbitration or trial cases. Diocletian's reign marked the end of the classical period of Roman law. And while Diocletian's system of rescripts showed adherence to the classical tradition, Constantine's jurisprudence was full of Greek and Eastern influences.

Diocletian reformed and organized the Roman army that had emerged from the great crisis of the third century. He merely continued the work begun by Gallienus and the Illyrian emperors (from Aurelian to Marcus Aurelius Probus to Marcus Aurelius Carus). Some of his acts had already been partly preceded by the desired transformations of his predecessors, but Diocletian set up an organic reorganization.

Diocletian's real great military reform was primarily political. The new emperor arranged, first of all, a division of the supreme imperial power, first through a diarchy (two Augusti, beginning in 286), and then through a tetrarchy (in 293, through the addition of two Caesars), thus accomplishing a first real "revolution" on the entire organizational structure of the Roman army since Augustus. This four-party form of government, while not so happy in the transmission of power (see subsequent civil war), nevertheless had the great merit of dealing promptly with external dangers to the Roman world.. Indeed, the presence of two Augusti and two Caesars facilitated rapid armed intervention and reduced the dangers that the prolonged absence of a single ruler could pose to the stability of the Empire.

Diocletian created a veritable new military hierarchy right from the highest state offices, those of the "four" emperors, where the highest in rank was the Augustus Iovio (protected by Jupiter), assisted by a second Augustus Herculio (protected by a demigod, Hercules), who was joined by the two respective Caesars, or "designated successors." In essence, this was a political-military system that made it possible to better divide the tasks of border defense: each tetrarch, in fact, took care of a single strategic sector and his administrative headquarters were as close as possible to the borders he was supposed to control (Sirmio and Nicomedia in the East), in this way it was possible to quickly crush the barbarians' attempts at incursion, preventing them from becoming catastrophic invasions such as those that had occurred in the 3rd century.

The new defensive system of borders was made more elastic and "deeper": to the rigid defense of the vallum was added an increasingly dense network of internal castella, connected by a more complex road system (one example above all: the strata Diocletiana in the East). In essence, there was a shift from a "linear" to a "deeper" defensive system (although not to the proportions generated by the crisis of the 3rd century, when Gallienus and the Illyrian emperors had been forced by the constant "breakthroughs" of the limes to resort to strategic "reserves" very much "inside" the imperial borders), which saw a major expansion of the "thickness" of the limes, which was extended from an inner belt of imperial territory to an outer belt in Barbaricum through the construction of numerous fortified "bridgeheads" (even across the great Rhine, Danube and Euphrates rivers), outposts with associated communication routes and logistical facilities.

A consequence of this transformation of the frontiers was also an increase in the protection of new and old military structures, which were adapted to the new defensive needs (this need was not so urgent in the first two centuries of the Roman Empire, which were mainly devoted to the conquest of new territories). New fortresses thus began to be built, or rebuilt, more compactly in their size (reducing their overall perimeter), more solidly in the thickness of their walls (in some cases they went from a thickness of 1.6 meters to 3.4 meters, as in the case of the Sucidava fortress) and with greater use of external towers, to improve their defense.

It is also true that from an archaeological point of view it is difficult to distinguish which fortifications were put in place by Diocletian and which by his predecessors and successors. The "Devil's Dyke," for example, the embankment built east of the Danube and traditionally attributed to Diocletian, cannot be dated with certainty to a particular century. What we can say about the structures built in this emperor's time is that:

In an attempt to solve the difficulties and slowness with which orders were transmitted to the frontier, the new imperial seats of the tetrarchic system were placed closer to the borders than Rome had been in the past: Augusta Treverorum was near the Rhine, Sirmium and Serdica were close to the Danube, Thessalonica was along the road leading to the East, and Nicomedia and Antioch were important locations in relations with neighboring Persia.

While Lactantius was critical of Diocletian for his excessive increase in the headcount of the Roman army, declaring that "each of the four had vastly more soldiers than any other emperor had ruled the state alone"; he is praised by the historian Zosimus, who describes his apparatus quantitatively concentrated along the frontiers, unlike Constantine, who concentrated it in the cities.

Both of these views had some truth to them, despite the biases of their authors: Diocletian and the tetrarchs greatly strengthened the army, and growth occurred especially in the border regions, where the increased numbers of the new Diocletian legions seem to have been distributed through a dense network of fortresses. However, it is difficult to establish the precise details of these changes, given the scarcity of sources. The army reached about 580000 men by 285 (when it consisted of 390000 armed men), of whom 310000 were positioned in the east, mainly along the Persian frontier. The fleet was increased approximately from 45000 to 65000 men. The Byzantine author, John Lydus gives us extraordinarily precise troop numbers: 389704 in land troops and 45562 in sea troops. His accuracy has greatly intrigued modern historians. Some believe that Lydus found these figures in official documents, and therefore they are credible and real; others believe instead that they are pure invention.

Diocletian, in essence, not only undertook a policy in favor of increasing manpower, but also aimed at improving and multiplying the military constructions of the period, although these were found, on the basis of archaeological findings, to be fewer in number than the ancients told

The expansion in the number of soldiers and civil servants forced the imperial system to have to provide for it with additional taxation. And since the maintenance of the armies involved the largest portion of the state budget, any reforms were particularly costly. The percentage of the population of adult males, excluding slaves, serving under arms rose from one twenty-fifth to one fifteenth, an increase deemed excessive by some modern historians. Troop wages were kept at low levels, so much so that most men often resorted to extortion or filling normal jobs among civilians. Arrears became a constant for most troops, many of whom were even paid in kind in lieu of receiving regular pay. And where it was not possible to pay this immense army, civil strife and riots often broke out. For this reason, Diocletian also had to reform the imperial system of taxation.

In the early imperial age (30 BCE to 235 CE), the Roman government paid for what it needed in gold and silver. The value of currency had thus remained almost stable. Forced purchase was used only when strictly necessary, to maintain the supply of armies during a military campaign. During the crisis of the third century (235-285), which had brought heavy economic and social consequences, the government often resorted to expropriation rather than payment in devalued currency, since it was not possible to tell what the real value of money was. Expropriation had a meaning equal to that of seizure.

Diocletian carried out a kind of confiscation in the form of taxation. He introduced an extensive system of taxes based on individuals (capita) and land (iuga) and tied it to a new and regular census of the empire's population and wealth. The officials of this census traveled throughout the empire, assessed the value of each landowner's labor and land, and combined the value of all landowners with the total of the entire population living in the city, with the aim of having an overall assessment of all the capita and iuga in the entire empire. This was a true annual state budget. The iugum was not a true land measurement. It varied according to the type of land, its harvest, and was also related to the amount of labor required for subsistence. Caput also depended on the type of people surveyed: for example, a woman was often valued as a half caput, or at any rate a different value from a full caput. Cities had to provide animals, money, and labor in proportion to their capita, and grain had to be provided in proportion to their iuga. The recruitment fee was called praebitio tironum, and could be paid in kind (by enlisting recruits from among a landowner's laborers) or, when a capitulum was extended to many farms, farmers helped pay the neighbor who was forced to provide recruits. Landowners in the senatorial order also had the option of paying taxes by a payment in gold (aurum tironicum). This form of taxation was called capitation.

Most taxes were paid on September 1 of each year, and were collected from each landowner by the decuriones. They had a role similar to that of municipal councilors, and were responsible for paying out of their own pockets for what they failed to collect. Diocletian's reforms also increased the number of financial officials in the provinces: more rationales and magistri privatae are attested under his reign than under his predecessors. These officials were tasked with managing the interests of the treasury, which collected taxes in gold, and imperial property. Fluctuations in the value of currency, meant that the collection of taxes was usually done mostly in kind, although everything was then converted into currency, taking inflation into account. In 296, Diocletian issued an edict reforming census procedures. It introduced a census every five years over the entire empire, thus replacing previous censuses and assessing changes in the value of new capita and iuga.

Italy, which had long been tax-exempt, was included in the new tax system by 290

Diocletian's edicts emphasized the common responsibility of all taxpayers. Public tax records were made public. The position of decurion, a member with city council, was an aspiration for wealthy aristocrats and the middle class, who showed their wealth by paying for city services and public works. But when decurions became responsible for any shortfall in tax collection, many tried to find ways to evade these obligations.

Aurelian's attempt to reform the coinage had failed; the denarius was dead. Diocletian had restored the system based on the three-metal coinage and issued coins of better quality.The new system was based on five coins: the aureus

By 301, however, the system was in trouble, hit by a new inflationary onslaught. Diocletian, in order to contain its effects issued the Edict on Maximum Prices (Edictum De Pretiis Rerum Venalium), an act that generated a new tariff schedule on all debts so that a nummus, the most common circulating currency, was depreciated by half. In the edict, preserved for us in an inscription from the city of Aphrodisia in Caria (near Geyre, Turkey), it was declared that all debts incurred before September 1, 301, were to be repaid with at the old value, while all debts incurred after this date were to be repaid at the new value. The edict was made to preserve the current price of gold and maintain coinage on silver, the traditional metal of Roman coinage. This edict risked giving a new impetus to inflationary growth, just as had happened after Aurelian's monetary reform. The response of the central imperial government had been to attempt to freeze prices.

The Edict on maximum prices was issued two or three months after the one on monetary reform, between November 20 and December 10, 301. The best preserved inscription that has survived to us is the one discovered in eastern Greece, although the edict survives in many versions, on different materials such as wood, papyrus and stone. In the edict, Diocletian declared that the crisis of that moment in history was mainly to be attributed to the uncontrolled greed of merchants, which had brought severe hardship to the mass of ordinary citizens. The language of the edict recalls the benevolence of the tetrarchs toward their own people and urges them to enforce the provisions of the decree in order to restore perfection in the world. The edict goes on to list in detail over a thousand consumer goods and urging them not to exceed various retail prices. Penalties were provided against those who transgressed these price tables.

These measures, however, were unsuccessful: the new currency quickly disappeared from the market as people preferred to keep it (hoarding), and the prices set caused some goods to disappear from the official market to be sold on the black exchange, so Diocletian himself was forced to withdraw the edict. In the meantime, however, the population's living conditions worsened: taxes were extremely heavy and many abandoned their productive activities, which were no longer profitable, often to live as beggars. Diocletian then resorted to preceptorship, that is, the obligation for the inhabitants of the empire to continue their trade and the denial of free choice of profession, forcing the inhabitants of the Roman empire to take over from their fathers in their productive activities.

In the most basic terms, the edict was ignorant of the laws of supply and demand: it ignored the fact that prices could vary from region to region, depending on the availability of products, and it did not take into account the cost of transportation in the retail price. In the judgment of historian David Potter, the edict was "an act of economic madness." The edict began with a long, rhetorical, moralizing preamble that understood little about economics and, by simply criminalizing a common practice, hoped to remedy the period's severe crisis.

There is no consensus on how actually the edict was imposed. Presumably on the one hand inflation, speculation, and monetary instability continued to persist, going to fuel a black, unofficial market generated by those goods where the price was imposed in the edict. The sanctions of the edict were applied very differently in different parts of the empire (some scholars believe that they were applied only in the part of the empire placed under Diocletian's rule), everywhere with great resistance, then disregarded perhaps as early as a year after the issuance of the edict. Lactantius wrote of the perverse manner in which the edict was enforced; of goods withdrawn from the market, of fights over minor price changes, of deaths when the provisions were enforced. This account may be true, although to modern historians it appears exaggerated and hyperbolic, considering that the legislative impact was not recorded in any other ancient document.

Also in response to economic pressures and in order to protect the vital functions of the state, Diocletian restricted social and occupational mobility. Peasants turned out to be tied to the land in such a way that this presaged a later system in which occupations turned out to be hereditary, as in the case of landowners or the occupations of bakers, gunsmiths, entertainers in show business, and mint workers. Soldiers' sons were forcibly conscripted, something that later became a spontaneous trend but also expressed the growing difficulties in recruiting armies.

The last years (303-313)

Diocletian entered the city of Rome in early November 303. On November 20, he celebrated with Maximian the twentieth anniversary of his own rule (vicennalia), the tenth anniversary of the tetrarchy (decennalia), and the triumph for the victory he had achieved over the Persians. He soon became impatient with the city, for the Romans had towards him, as Edward Gibbon points out, based on what Lactantius has handed down to us, a "licentious familiarity." The Roman people did not have sufficient deference to his supreme authority; they expected him to play the part of a democratic ruler, not a monarchical one. On December 20, 303, Diocletian decided to leave the capital, disappointed (after also viewing the construction of the largest Roman baths, dedicated to him), and went north. He did not even wait for the ceremony that would invest him with the ninth consulship; he did so instead in Ravenna on January 1, 304. According to accounts in the Panegyrici Latini and Lactantius, Diocletian arranged for his and Maximian's retirement from political life, abdicating in favor of the two caesars. Maximian, according to these accounts, swore to uphold the wishes of Augustus Jovius in a ceremony held in the temple of Jupiter Optimus Maximus.

From Ravenna, the same left for the Danube. There, probably in company with Galerius, he took part in a military campaign against the Carpi. He fell ill during this time, and his health deteriorated rapidly, so that he had to be transported by litter. In late summer he left for Nicomedia. On November 20 he appeared in public to inaugurate the new circus in front of the imperial palace. He collapsed immediately after the ceremonies. During the winter of 304

Galerius arrived in the city later in March. According to what Lactantius tells us, he came armed with the intention of reconstituting the tetrarchy, forcing Diocletian to resign and placing men of his trust in the imperial offices. He seems to have threatened Augustus himself, so much so that he eventually succeeded in convincing him to comply with his plan. Lactantius also claims that he did the same to Maximianus at Sirmio. On May 1, 305, Diocletian summoned his generals, traditional comites and representatives of their respective legions to an assembly. They all met at the same hill, three miles from Nicomedia, where almost twenty-one years earlier Diocletian had been proclaimed emperor. In front of the statue of Jupiter, his patron deity, Diocletian addressed the crowd with tears in his eyes. He spoke to them of his weakness, his need to rest and retire. He declared that there was a need to pass the command to someone stronger than himself. He thus became the first Roman emperor to voluntarily abdicate.

Most believe that they knew what would happen: Constantine, son of Maximian's Caesar Constantius Chlorus, and Maxentius, son of Maximian, the only adult sons of the reigning emperors, men who had long prepared to succeed their fathers, would be granted the title of Caesars. Caesar Galerius would have been excluded. Constantine had traveled through Palestine alongside Diocletian, and was present in the palace of Nicomedia in 303 and 305. It is likely that Maxentius, who instead resided in Rome, received identical treatment. In Lactantius' account, when Diocletian announced his resignation, the entire crowd turned to Constantine. It was not they, however, who were declared Caesars, as the chosen ones were Flavius Valerius Severus and Maximinus Daia. The latter appeared and took the robes of Diocletian. On the same day, Severus received those from Maximianus in Mediolanum (Milan). Constantius thus became the new Augustus of the West in place of Maximian, Galerius took over from Diocletian, while Constantine and Maxentius were totally ignored in the new transition of power. This did not bode well for the future security of the tetrarchic system.

After a solemn ceremony, he deposed the office and title of Augustus on May 2, 305, and retired to a marvelous palace built especially for him in Split, not far from Salona, the important provincial center of Dalmatia (now in Croatia). It was a heavily fortified structure by the Adriatic Sea. Maximian, on the other hand, retired to a villa in Campania or Lucania. Their new residences were distant from political life, but the two ex-augusts were close enough to remain in close contact with each other. Galerius assumed the consular fasces in 308 with Diocletian as his colleague. In the fall of that year, Galerius asked Diocletian to attend a conference at Carnuntum (now Petronell-Carnuntum, Austria). The two ex-augusts went to the legionary fortress on the Danube, where this meeting was held on November 11, 308, at which Galerius replaced the late Augustus Severus (Constantius had died in 306) with Caesar Licinius, since Severus had been killed by Maxentius, who had proclaimed himself Augustus in Rome with the support of the Senate. Diocletian forbade Maximian from having any new aspirations to the imperial purple after his retirement, which was to be understood as final. At Carnuntum, many begged Diocletian to resume power, to resolve the conflicts that had arisen with the rise to power of Constantine, who had been appointed Western Caesar by his father's legions, and the usurpation of Maxentius against Severus and Licin

At Carnuntum the tetrarchic hierarchy was, therefore, peacefully established for the last time:

Maxentius was recognized as usurper for the umpteenth time and Maximian forced to retire to private life. Interestingly, in the East the power of the tetrarchs was firmly in place, while in the West the usurpers Maxentius and Domitius Alexander ruled, respectively, over Italy, Sicily, Mauretania, and Tripolitania the former, and Sardinia, Proconsular Africa, and Numidia the latter. In Galerius' plans, the newly-august Licinius was tasked with regaining the territories usurped by Maxentius and Domitius Alexander. Maxentius also defeated Alexander preparing for his clash with Constantine.

Diocletian spent the last years of his existence in the gardens of his palace. He saw the Tetrarchic system fail under the blows of the ambitions of his successors: the revocation of the anti-Christian edict by his son-in-law and successor Galerius (who was succeeded by Maximinus as Augustus of the East), and the edict of toleration by the new Augustus of the West, Constantine (with Licinius moving to the East by ousting Maximinus Daia), who defeated and killed Maxentius at the Milvian Bridge. He also learned of Maximian's third attempt to regain imperial power, his forced suicide, and his damnatio memoriae decreed by Constantine in 310, which in part also affected his person, since in many statuary and pictorial portraits Maximian and Diocletian were depicted together. He was still alive in early 313, when he was invited by Constantine to the wedding of his sister Constance and Licinius, celebrated in Milan in February of that year. He died a few months later, probably between March and April (at about age 70), at any rate before the defeat of Maximinus, the ousted regular Augustus of the East, which occurred in the summer of 313 at the hands of Licinius. His wife Prisca (who separated from Diocletian in 305) and daughter Galeria Valeria (with grandson by marriage), entrusted to Licinius after Galerius' death, fled to Maximinus, who then exiled them to Syria; they were later had killed by Licinius in 315, extinguishing Diocletian's family. Having now dissolved the tetrarchy with its creator still alive, within a decade Constantine also ended the new diarchy, defeating and having Licinius killed as well (324), and remaining sole emperor. Diocletian was buried in his palace in Split, later being officially deified with apotheosis and an imperial cult dedicated to him.

In the 18th century, Abruzzi chroniclers including Pietro Pollidori, Domenico Romanelli and Don Uomobono Bocache, began to argue in their history writings for the construction of the ancient bridge of the Roman Anxanum dei Frentani, commissioned by Emperor Diocletian to facilitate passage over the Pietroso ditch from the city to the meadow of the Fairs, where local trade was conducted. As Florindo Carabba recalls, even Don Bocache is said to have found during the reconstruction work of the Cathedral of Our Lady of the Bridge, the plaque attesting to the construction at the behest of the Senatus Anxanense. The Bridge in the 1990s was the subject of archaeological excavations at the behest of the Superintendence of Chieti, and archaeologist Staffa is said to have found a portion of the Roman bridge head, attached to the head of the 14th-century medieval bridge, and the Diocletian auditorium area has been musealized.

Sources

1. Diocletian
2. Diocleziano
3. ^ Barnes 1982, p. 4.
4. Timothy D. Barnes, "Lactantius and Constantine", σελ. 32-35, The Journal of Roman Studies 63 (1973)
5. Né Dioclès (Διοκλῆς / Dioklês) et latinisé en Diocletianus (Dioclétien).
6. Des pièces sont émises en son nom en Cyzique vers la fin de 284, mais il est impossible de savoir s'il est encore présent publiquement à cette date. Voir Roman Imperial Coinage 5.2 Numerian no 462 ; Potter The Roman Empire at Bay : AD 180–395, p. 279-280.
7. Zum inoffiziellen Praenomen Marcus vgl. L’Année épigraphique 1965, 315: Αύτοκράτορα Καίσαρα Μᾶρκον Αύρήλιον Γάϊον Ούαλέριον Διοκλητιανόν Εύσεβῆ Εύτυχῆ Σεβαστόν.
8. Als Todesjahre Diokletians werden in der Forschung 311, 312, 313 und 316 diskutiert. Alexander Demandt geht von 316 aus und begründet dies ausführlich in Alexander Demandt: Diokletian. Kaiser zweier Zeiten. München 2022, ISBN 978-3-406-78731-7, S. 315–317.
9. Der Geburtsort ist nicht sicher; vgl. Wilhelm Enßlin: Valerius Diocletianus. In: Paulys Realencyclopädie der classischen Altertumswissenschaft. Band 7 A, 2 (1948), Sp. 2419 ff., hier Sp. 2420 f.
10. Chester Beatty Papyri. Papyri from Panopolis in the Chester Beatty Library, Dublin. Hrsg. von T. C. Skeat. Dublin 1964, S. 86f.
11. Eutrop, Breviarium 9,19.