The First Tetrarchy (293–305 CE)

Abstract

This chapter continues with the description of Diocletian’s and Maximian’s careers, starting from the year in which the tetrarchy was born (293), when two men from Illyricum, namely Constantius and Galerius, were appointed as junior emperors, or caesares. This chapter describes the tetrarchy as a brand new political system, examining relations between its senior and junior emperors, as well as their areas of responsibility, their residences, and travels. After discussing important political events during the first tetrarchy, the narration focuses on Diocletian’s monetary, price, and tax reforms, as well as reforms concerning the new administrative structure of the empire (the evolution of the praetorian prefecture in particular, but also the creation of dioceses, and the changes in the army). This chapter concludes with the persecution of Christians during the first tetrarchy.

The Establishment and Functioning of a New Political System

A fair few people could tell you that “tetrarchy” is of Greek origin and means “rule of four”. Not quite so many know that the word was in use long before Diocletian’s time. Fewer still are privy to the fact that Diocletian and his colleagues did not call themselves “tetrarchs” at all. It could even be argued that they would have been offended had anyone called them a tetrarch, as this was a term reserved for the subordinate rulers of Rome in the East at the turn of the Common Era.¹ Their titles were clearly dictated by tradition: imperator and augustus designated a senior emperor, caesar a junior emperor.² Modern historiography employs the term “tetrarchy” not only for the sake of simplicity, but also to place a stress on the administrative—rather than political—division of the Roman Empire into four parts. The first tetrarchy began precisely on 1 March 293, when Constantius and Galerius were added to the existing two emperors, Diocletian and Maximian, as co-rulers, thus creating a system of two senior (augusti) and two junior (caesares) emperors.

It is disputed when the tetrarchic system as such ended. The name “second tetrarchy” is usually applied to the brief period between the abdication of Diocletian and Maximian and the death of Constantius I (1 May 305–25 July 306). Starting with the usurpations by Constantine and Maxentius in late 306, the tetrarchic system began to collapse, and we could question how much sense it makes to refer to emperors ruling in different parts of the empire in the following years as tetrarchs (because, if nothing else, there were not always four of them). And yet we find the term “third tetrarchy” sometimes used for the period 306–308, and even the “fourth tetrarchy” for the years 308–310.³ As far as Simon Corcoran is concerned, “the tetrarchy proper, of two Augusti and two Caesars, only functioned from 293 to 306 and ceased entirely once all the rulers held the full rank of Augustus by 310”.⁴ However, it could be argued that the idea of tetrarchy had been dealt a fatal blow as early as the usurpation of imperial power in 306 by Constantine and Maxentius, as the two “princes” entertained ambitions on a scale not foreseen by the tetrarchic system.

Scholars debate whether the tetrarchy was masterminded by Diocletian from the ground up, or whether it actually evolved spontaneously and was the product of many factors, of which Diocletian’s idea was just one. Nor can we be sure whether Diocletian had always had a plan on how to deal with the problem of succession. As we know, both caesares were promoted to augusti in 305 to fill the void left by their former superiors’ political retirement. Had this eventuality been anticipated by Diocletian back in 293?⁵ And just when did he come up with his plan for voluntary abdication? Clearly, here at least, Diocletian must have been making preparations several years in advance: although we do not know when work started on the construction of his “retirement” palace in present-day Split, it was evidently intended as a place of rest and relaxation for a private citizen, not an emperor.⁶

The initial division of power between Diocletian and Maximian in 285, the causes of which have already been discussed here, was unquestionably revolutionary in that it paid no heed to blood kinship (unlike the practice established under the Julio-Claudian and Flavian dynasties), and very probably also disdained “institutionalised adoption” (on which the second-century “adoptive emperors” of the Antonine dynasty had relied so heavily).⁷ As Stephen Mitchell points out, Diocletian’s “main objective was to achieve a manageable division of imperial powers, and it led to an unofficial territorial division of the empire”.⁸ The very same could be said of the emergence of the tetrarchy per se in 293. It is best summed up by Warren Treadgold: “to give each weak point in the frontier a capable commander who would not proclaim himself emperor, by 293 Diocletian chose three trusted generals and proclaimed them emperors himself”.⁹ Considerations of security and political stability plainly played an important role in Diocletian’s thinking: after 285, it was unlikely that any usurper would triumph over legitimate emperors; after 293, it was all but impossible.

This division of the empire was not political, but purely administrative, a distinction that is obviously very important. Political division had always spelt disaster for the empire as a whole, and the Palmyrene Empire and the “Gallic Empire” would still have been fresh in the minds of Diocletian and all his colleagues. Diocletian was actually determined to keep the empire united politically, protected from the enemy both without and within. While his choice of co-rulers was intended to ease his own daunting task of protecting, administering, and reforming a Roman Empire that had only just begun to recover from the crisis of the third century, it was also designed to prevent usurpation, instability, and chaos. Indeed, these efforts coloured absolutely everything Diocletian did during his 20-year reign.

The new system that Diocletian gradually crafted was not entirely contrary to the two aforementioned political systems that had previously ensured the continuity of imperial power: adoption, marriage, and even blood kinship still had a role to play in the tetrarchy as well, as we shall see later. Yet, at its core the tetrarchy was—or certainly should have been—a meritocracy, a system that placed a premium on merit, personal qualities, and loyalty. Diocletian, as the architect of the whole system, undoubtedly retained control over it throughout the duration of the first tetrarchy. Therein lay its strength, but also its weakness. The tetrarchy did not long outlive its creator and can be said to have failed; indeed, it was arguably doomed to run aground.¹⁰ In our evaluation of this system, what matters is the yardstick by which we measure success. For Aurelian, who ruled for 5 years and managed to unite the empire politically for the first time in ages, to have stayed in power for 15 years would have been a fantastic achievement. Gallienus, who did rule for 15 years, would surely have considered it a great access had he ruled the whole empire. Then there is Diocletian, who did rule the whole empire—with a firm hand—for 20 years. In that time, he defeated all external and internal enemies, ceded no territory (on the contrary, he actually gained a little in the East), reorganised the empire’s political, administrative, monetary, fiscal, and legal systems, ensured its future economic, social, and military stability by making the necessary reforms, and introduced the unheard-of notion of planned abdication. Even with the benefit of hindsight, we would have been unable to advise Diocletian on how better to maintain the system of tetrarchy he had created or how better to secure the empire politically in the future.¹¹

Genealogical Chart 4.1

Genealogy of Constantine’s line together with the “extended tetrarchic family”

The First Tetrarchy (293–305 CE): The Emperors and Relations Between Them, Their Travels, and Their Cities of Residence

As we have already noted, Constantius and Galerius became caesares on 1 March 293. Constantius was elevated in Milan on the authority of the Western augustus Maximian, while Galerius was elevated personally by Diocletian, probably in Sirmium.¹² Constantius was senior in rank to his colleague Galerius, even though they were appointed caesar on the same day. The difference lay in their age: Constantius was older than Galerius (by some 15 years, according to Leadbetter).¹³ This is why his name is always given before Galerius in official documents. Each of the two new caesares was in a subordinate position to his elder augustus in terms not only of the power hierarchy, but also kinship, since each was the son-in-law of his augustus—Galerius was given Diocletian’s daughter Valeria as his wife, and Constantius married Maximian’s daughter Theodora.

Some sources refer to Theodora as Maximian’s stepdaughter (privigna).¹⁴ In that case, she may have been his wife Eutropia’s daughter from an earlier marriage. But who was Eutropia’s previous husband? One of Theodora’s sons was named Hannibalianus, leading some to speculate that Eutropia’s husband had been the praetorian prefect Afranius Hannibalianus (with whom we shall become more acquainted below), while others consider Theodora more likely to have been Maximian’s own daughter, born to him from his previous marriage to Hannibalianus’ daughter.¹⁵

Naturally, Galerius and Constantius had to divorce their previous wives before marrying the daughters of their respective augusti.¹⁶ However, no formal annulment of the marriage may have been necessary. As we shall see in the next chapter, Constantius and Helena were very probably joined only in a common-law marriage. Despite perhaps never becoming Constantius’ legally recognised wife, Helena bore him a son, Constantine, evidently in 272 (see the next chapter for a discussion on the problem of the year of Constantine’s birth). This would suggest that Constantius already had a 21-year-old heir when he was proclaimed caesar. We have no idea who Galerius was previously married to, if at all. What we do know is that he had two children, Candidianus and Valeria Maximilla. Lactantius describes Candidianus as Galerius’ illegitimate son, even though he was not born until 295 or 296¹⁷; indeed, he was born to him by a concubine, apparently with the consent of Valeria, who was herself barren and subsequently adopted Candidianus.¹⁸ Valeria Maximilla was married to Maxentius, Maximian’s son, sometime before 304,¹⁹ so she must have been much older than Candidianus—by 10–15 years—and it is very likely that she, too, was Galerius’ daughter by a previous marriage or concubinage.²⁰

As to the names of the two caesares, Galerius’ original name was probably Maximinus,²¹ but he was now C. Galerius Valerius Maximianus; Constantius’ full name was now Flavius Valerius Constantius.²² We have already touched on the possibility that Maximian was adopted by Diocletian (filius Augusti) in 285; at any rate, he then added Diocletian’s name Valerius to his own and styled himself Marcus Aurelius Valerius Maximianus. But the situation changed when Maximian became augustus, and we are suddenly told that he was Diocletian’s “brother” (frater augusti Diocletiani).²³

Relations between members of the tetrarchy were hardly built on concordia and harmony. Although Maximian had always been loyal to Diocletian, relations between the two new caesares were, as we shall see, less than ideal, with Bill Leadbetter noting that “although Diocletian had selected both of these men, neither of them had selected the other”.²⁴ The tetrarchs’ divine names also pose a problem. We have already seen how Maximian took on the cognomen Herculius (evidently as early as 286, perhaps a year later), while Diocletian emphasised his superior status by giving himself the name Jovius. Every subsequent legitimate tetrarch ruling in the West was Herculius; every subsequent tetrarch in the East was Jovius. When it came to the naming of the caesares, the younger Galerius was endowed with the “higher” cognomen of Jovius, while Constantius, his senior in both service rendered and age, was merely Herculius. Regardless of any symmetry of power, the West was clearly to be associated with Hercules, while the East was to be identified with Jupiter. Hence, Maximinus Daia and Licinius also received the cognomen Jovius, while Severus and Constantine were given the name Herculius.²⁵

Why were Constantius and Galerius chosen for the first tetrarchy? Constantius, praeses Dalmatiae in 285, appears to have been a friend and confidant of Maximian and was probably called to the West and assigned important duties not long after Maximian came to co-rule. Before his elevation to caesar, he must have held some powerful office in the West, though we do not know what it was.²⁶ Galerius was born into a peasant family in (what was to become) the province of Dacia Ripensis.²⁷ His mother Romula is said to have fled to this area south of the Danube from Roman Dacia,²⁸ but we do not know exactly when; it may have been in the early 250s.²⁹ Later, when Galerius was on the throne, he would name his hometown after his mother (Felix Romuliana), build a palace there—in imitation of Diocletian—and be buried there.³⁰ The archaeological remains of this city are located near Gamzigrad, a site near the town of Zaječar in Serbia. While the year of Galerius’ birth remains unknown to us, we can posit that he was the youngest member of the first tetrarchy. Joannes Malalas says that Galerius died at the age of 53, which would make his birth year 258, since he died in 311. Malalas’ account of the tetrarchy may be very muddled and riddled with errors (e.g. he calls Galerius “Maxentius Galerius” and has him assassinated in Rome), but his information on Galerius’ age at death falls within the bounds of possibility, so we can work with the hypothesis that he was born in 258; this would also be consistent with the supposed years in which his two children were born.³¹ Galerius was nicknamed Armentarius, “the Herdsman”, for that is what he originally was.³² Our aristocratic sources may turn up their noses at the very humble origins of Galerius and his parents, but Diocletian chose his fellow rulers on account of their proven ability and personal loyalty (both of which Galerius showed in abundance during his reign), not where they came from.

During the first tetrarchy, the empire was not split politically. It is also difficult to discern its territorial and administrative divisions at this time, especially in the East, because the two Eastern tetrarchs’ spheres of competence are hazy. Modern scholars who have a go at defining those responsibilities rely on Aurelius Victor, who says that Constantius “was entrusted with everything north of the Alps, Maximian with Italy and Africa, Galerius with Illyricum as far as Pontus, and Diocletian retained the rest”.³³ Aurelius Victor, though, was writing from the perspective of the late Constantinian dynasty, when the internal boundaries of the empire had been delineated—as opposed to the first tetrarchy, when they were evidently not defined at all. In this light, his testimony should be taken with a pinch of salt. If we were to take him literally, we could end up making mistakes and declaring, for example, that Galerius “acquired Illyricum, with a residence in Sirmium”,³⁴ when in fact, if our sources allow us to determine anything, it is that Galerius’ seat of residence was first Antioch and only later Thessalonica and Serdica (present-day Sofia, Bulgaria). Not to mention the fact that Galerius was a frequent traveller. Sirmium may have been the place where Galerius was elevated to the rank of caesar, but otherwise his presence here is not attested; on the contrary, this is the city where Diocletian would often spend the winter.³⁵ Caution is also advised when describing Galerius’ defined sphere of competence. If we accept Victor’s claim that Galerius was commissioned by Diocletian to defend the Danube frontier while himself taking charge of the East, i.e. Asia Minor, Syro-Palestine, and Egypt, then we have to concede that Galerius, in the first six years of the tetrarchy, was somewhere he should not have been, since we are more likely to find him in Antioch, Egypt, or Mesopotamia; his presence on the Danube frontier can only be established from 299 onwards.³⁶ And in Diocletian’s case the situation is even more complicated.

Of the emperors of the first tetrarchy, Diocletian, at least in the first period of his reign, was easily the most active traveller.³⁷ Broadly speaking, we find him not only in the Balkans, Asia Minor, Syria, and Egypt, but also on the Middle or Upper Danube and, several times, in Italy. Often, though by no means every year, he and his court wintered in Nicomedia in Asia Minor or in Sirmium by the Danube. The court that travelled with Diocletian was bound to have included not only officials and servants, but also elite troops and a corps of protectores; several thousand people must have been involved.³⁸ We can reconstruct the movements of his court in some years very accurately from our sources; at other times, we are left to conjecture. We can distinguish four phases. In 284–293, the emperor travelled through places as diverse and distant as Syria, Bithynia, Thrace, Pannonia, Raetia, and Italy. He was attempting to cover the entire Danube region without losing sight of the empire’s Eastern frontier. In 293–296, having entrusted the East to his caesar Galerius, he restricted his travels to the Balkans. In 296–302, Diocletian was forced further afield by the Persian War and a revolt in Egypt, spending time in Syria, Mesopotamia, and Egypt. Finally, in 303–305, he can be found in Nicomedia, whence he made a single but significant journey: from mid-303 to mid-304, he travelled along the Danube to Italy and then back again.

The “laziest” tetrarch was probably Constantius, who kept the Rhine frontier secure from his base in Trier (he is rarely attested elsewhere in Gaul), waged war twice in Britain (in 296 and 305–306), and, aside from one visit to Italy, never ventured beyond his assigned territory. His augustus, Maximian, also initially resided in Trier during the dyarchy, but in 293 he left this residence to his caesar and thereafter resided mostly in Milan and Aquileia in northern Italy, but also in Ravenna, Verona, and Rome; in 296, he was on the Rhine and in Hispania, and in the following three years he was in Africa. Victor’s assertion holds true, at most, for the West, where, from 293 onwards, the two tetrarchs more or less stuck to their respective parts of the empire and, by all accounts, did not interfere with each other’s jurisdiction or travel East. In the East, on the contrary, the most we might say is that there were very flexible boundaries of temporary territorial responsibility. Moreover, only Galerius was bound by them, as Diocletian retained global responsibility. David Potter rightly argued that any formal division of the empire would have run counter to the ideology of the tetrarchy, which required the members of the imperial college to work as a team.³⁹ Half a century later, the emperor Julian, in Caesares, described the members of the first tetrarchy as a close-knit club in which Diocletian alone occupied a privileged place.⁴⁰

Another problem is the cities where the tetrarchs resided. Some scholars assert that the main (but not the only) residences of the tetrarchs were essentially Nicomedia (for Diocletian), Thessalonica (Galerius), Milan (Maximian), and Trier (Constantius),⁴¹ but even if we were to accept this, we still need to stress that this is nothing but a sweeping statement trying to bring order to chaos and sum up the 20 years of the first tetrarchy. It would be more accurate to say that the empire had 6–8 main centres at the time of the first tetrarchy (Sirmium, Nicomedia, Antioch, Milan, Aquileia, Trier, and later Thessalonica and Serdica) and that at least two of them (Antioch and Nicomedia) may have been shared residences for a time: Galerius and Diocletian are attested in Antioch in the spring of 299 and again in Nicomedia at the turn of 303. As for the West, Diocletian and Maximian held talks together in Milan in late 290 and 291 and met in Rome in late 303. Rome had ceased to be an imperial residence and seldom hosted an emperor at all. Throughout the first tetrarchy, it was visited only by Diocletian and Maximian, the former at most twice and the latter about four times.

Everywhere the emperor went, his court was sure to follow. The core of Diocletian’s court, like that of his predecessors, was the imperial council (consilium principis).⁴² Here, the emperor’s advisers and friends were joined by a group of senior officials from the equestrian order, who were responsible for the central authorities’ various secretariats. By this time, these bureaux had come to be known as scrinia, and the people in charge of them also had new titles: the official whose duty was to answer petitions from private persons (a libellis) was now called magister libellorum; the heads of offices responsible for formulating the emperor’s letters to cities, governors, and other officials in Latin (ab epistulis latinis) and Greek (ab epistulis Graecis) were called magister epistularum Latinarum and magister epistularum Graecarum, respectively; and the scrinium memoriae, which we would think of as archives, was managed by the magister memoriae (formerly magister a memoria).⁴³ Two officials were in charge of financial matters: the administration of public finances (including mints and precious-metal mining) was overseen by the rationalis summae rei⁴⁴; the imperial estates (“the property of the crown”), once administered by an official called a patrimonio, were now managed by the rationalis rei privatae.⁴⁵ As the importance of these offices dwindled when inflation took hold in the third century, the praetorian prefect—as the official responsible for supplying the army—saw his prominence rise. This effectively made the praetorian prefect a third (and the most important) finance minister, since most taxes were paid in kind (annona).⁴⁶

Important Political Events During the First Tetrarchy

As we saw in the previous chapter, soon after Maximian’s elevation to augustus there was a successful attempt to create a separatist empire in Roman Britain, with Carausius (286–293) and, after him, Allectus (293–296) exercising sovereign rule over this territory. Maximian was initially tied up elsewhere, as securing the Rhine and Danube frontiers was clearly a higher priority. Once he did get round to dealing with the British problem, his invasion of the island (289) floundered and the recapture of Britain was postponed. Although Constantius began to grapple with Carausius’ revolt immediately after his appointment as caesar, in 293 the most he succeeded in doing was cutting Carausius off from Gaul by retaking Bononia. A little later in that year, Carausius was assassinated by one of his own men, Allectus, who took over from him.⁴⁷ Constantius, in the meantime, had built a fleet and embarked on an expedition to the area between the Scheldt and the Rhine to campaign against the Chamavi and the Frisii.⁴⁸ After making careful preparations and drawing on the generous assistance of the praetorian prefect Asclepiodotus, he successfully invaded the island in 296 and Roman Britain was finally rejoined to the empire.⁴⁹

In the same year, revolutionary events began to unfold in the East. In the previous chapter, we discussed Diocletian’s diplomatic success in his handling of the Persians in the East in 287. With nothing of significance happening on the Persian frontier, he was free to concentrate on other problems. All this changed after the accession of Shapur I’s son, Narseh (293–302).⁵⁰ Determined to expunge the ignominy brought about by his nephew Bahram II, Narseh invaded Armenia—which Ammianus Marcellinus noted “rightfully belonged to the Romans”—in 296.⁵¹ King Tiridates III, installed in Armenia in 287 by Diocletian, now had to seek asylum in Roman territory.⁵² Narseh then headed south to Osroene. Diocletian, busy fighting the Carpi on the Danube, responded by sending his caesar Galerius, who was probably in Syria at the time, to confront the Persians while he himself raised reinforcements on the Danube and then also hastened to the East. With Narseh outnumbering Galerius, it may have been wiser to wait for Diocletian’s arrival, but we do not know what communication took place between the two emperors and what orders Galerius received. In any event, Galerius’ attempt at a counter-attack in the spring of 297 failed and he was defeated in battle between the cities of Carrhae and Callinicum in northern Mesopotamia. This handed Narseh control of Roman Mesopotamia. When Diocletian met Galerius in Antioch, he reprimanded him severely for his failure. In front of everyone, Galerius was made to walk (or run, according to some sources) a mile (or more) ahead of Diocletian’s chariot, despite being dressed in the purple robes of an emperor. This story (which may be a later invention) is told with slight variations by numerous authors. If the similar diction they employ is anything to by, they all drew on a single source (probably the Kaisergeschichte). Typically, Lactantius, who is not dependent on this source, knows of no such thing (and considering how much he loathed Galerius, he would have been only too happy to mention this humiliation).⁵³

However, since Diocletian himself was otherwise engaged in suppressing the revolt in Egypt (on which see below), he once again put Galerius in charge of this war. When Galerius invaded Armenia in 298, or perhaps as early as the autumn of 297, he took with him a good-sized army, mostly assembled from inhabitants of the Danubian provinces (Festus says he had 25,000 men). Narseh, accepting the challenge, marched against him. In all probability, the battle was fought somewhere east of the Armenian city of Satala in 298.⁵⁴ Galerius, who is said to have personally scouted the terrain in advance with only two horsemen, took the great king by complete surprise.⁵⁵ After his camp was raided, Narseh himself barely escaped the battle, but his entire family, including his wives, sisters, and children, not to mention the royal treasure, was captured. This opened up a path for Galerius to pass through Armenia, Media, and Adiabene, making his way along the Tigris until he reached Ctesiphon. While we do not know whether he plundered this city, we are told (by a later author) that the return journey took him along the Euphrates and past the fortress of Anatha (present-day Anah, Iraq).⁵⁶ By the end of 298, he had re-secured northern Mesopotamia for Rome and brought Armenia back within the Roman sphere of influence. Diocletian, who had meanwhile dealt with the situation in Egypt, met and congratulated his caesar in Nisibis in the spring of 299, and together they dispatched the terms of their peace treaty to Narseh.⁵⁷ The king had no choice but to accept their offer if he wished to get back his family (whom the Romans had treated with all due respect). The treaty included a new status for Armenia (the territory of which had been extended quite a way eastwards), designated Nisibis (now in Roman territory) as the only place of trade between the two parties, and, above all, forced Narseh to cede to Rome the five satrapies between the Tigris and Armenia. In other words, everything west of the Upper Tigris was now Roman.⁵⁸ This was the greatest victory achieved in the East since the time of Trajan. Most importantly, it secured peace there for a very long time: it would not be until 337 (under Constantine) that another war broke out with the Persians.

As for the revolt in Egypt, a certain Lucius Domitius Domitianus is attested as the usurper on papyri and coins. The trouble here is that literary sources are completely silent on him and instead mention that a rebel named Aurelius Achilleus usurped imperial power in Alexandria.⁵⁹ This Achilleus appears to have been a corrector under Domitianus.⁶⁰ This was a far-reaching rebellion that engulfed the whole province and took eight months to put down. Barnes reconstructs these events as follows: Domitianus usurped power in Egypt in late August 297; this usurpation was crushed and Domitianus was killed in December of the same year, but Achilleus continued the revolt in Alexandria; Diocletian was forced to besiege Alexandria, but did not succeed in taking it until several months later, probably in March 298.⁶¹ The later Byzantine historian John Malalas tells us an interesting story about Diocletian’s conquest of Alexandria. Diocletian is said to have ordered his soldiers to keep on slaying the people of Alexandria until the blood had risen to the knees of his horse. It just so happened that, upon entering the city, Diocletian’s horse stumbled over the corpse of an Egyptian. Its knee scraped against the dead body and was smeared with blood. The emperor, noticing this, ordered his men to stop the killing. The Alexandrians erected a bronze statue of the horse to show their gratitude. As late as Malalas’ time (the sixth century), the site of the statue was evidently known as “Diocletian’s Horse”.⁶² The emperor remained in Egypt for the rest of the year in order to make sure this territory was secure. He sailed up the Nile and made treaties with two tribes, the Nobatae and the Blemmyes. He ceded the territory south of the Syene to the former and charged it with defending Roman Egypt against the latter. He then began to make regular annual payments in gold to both.⁶³ It was probably on this occasion that the emperor administratively split Egypt into two provinces—Egypt proper and a southern part, Thebais (see below). Early in 299, he repaired to Syria and, as we know, met Galerius in Nisibis in the spring.

Williams takes a quite different view of the revolt, suggesting that it was aimed at gaining independence for Egypt, and for this reason the rebels are said to have allied themselves with Narseh. Aside from the fact that some Roman forces would have been tied up in Egypt in order to suppress the rebellion, it is not entirely clear what use Narseh would have had for such an alliance or what the rebels would have gained had Narseh taken Egypt. Dissatisfaction with high taxes seems a more natural and simpler explanation of the causes of the revolt.⁶⁴ Another controversial claim put forward by Williams is that Domitianus was merely a stooge and that the real leader of the rebellion was Achilleus all along, i.e. their roles as leaders were concurrent, not successive. This, too, is within the realms of possibility, but in the absence of evidence it must remain a mere hypothesis.⁶⁵

As mentioned in the previous chapter, the emperor Aurelian had previously moved part of the Carpi tribe into Roman territory. Our sources assure us that the tetrarchs completed the work by relocating the rest of this Dacian tribe into Roman territory, specifically Pannonia. What we do not know, however, is whether Diocletian or Galerius was responsible for this transfer, and there is also a problem with dating. Although Jerome and the Consularia Constantinopolitana are precise about the year, saying the Carpi moved in 295,⁶⁶ this seems too early. We need to take into account the Carpicus maximus victory title the tetrarchs awarded themselves repeatedly in 301–304.⁶⁷ If the tetrarchs had transferred the Carpi in 295, why did they bestow upon themselves this title four more times in succession at the beginning of the new century? Although the tetrarchs’ victory titles were essentially shared, i.e. the triumph of one member of the imperial college was presented as the victory of all four,⁶⁸ thus also avoiding unnecessary rivalry, it should not be difficult to determine who was responsible for the transfer by studying the recorded movements of the courts of the two Eastern tetrarchs and their spheres of responsibility. As we have seen, Galerius was in the East until at least 299, and it was only in the early fourth century that he could have taken over responsibility for the Danube frontier from Diocletian. If we accept the hypothesis that the repeated defeat of the Carpi and their subsequent relocation occurred in the early years of the fourth century rather than at the end of the third century, we can conclude that it was Galerius who relocated the Carpi, probably in 304.⁶⁹

Certain accounts of this event report that it was not just the Carpi that the tetrarchs moved to the empire; some of the Sarmatians and the rest of the Bastarnae (to join those who had already been displaced to Roman territory by Probus) were also resettled here, probably at the same time. Several sources attribute this to the tetrarchs in general,⁷⁰ others specifically name Diocletian and Galerius,⁷¹ and then there are three that ascribe the displacement of the Carpi to one (but not the same) emperor. Ammianus Marcellinus suggests that it was Diocletian who moved the Carpi, and even who tells us that Pannonia had been singled out for the resettlement.⁷² However, his account is rather ambiguous; Diocletian himself may not have attended to these operations personally, but may have delegated them to Galerius, as categorically stated by Jordanes⁷³ and, especially, Lactantius. The latter mentions that the later emperor Maximinus Daia is said to have surrounded himself with barbarians “who had been driven out of their lands by the Goths at the time the vicennalia were being celebrated, and who had surrendered to Maximian (i.e. Galerius) to the detriment of the whole human race”.⁷⁴ Diocletian and Maximian held these vicennalia, or 20th anniversary celebrations, in Rome in the autumn of 303,⁷⁵ and Lactantius is very likely to have had the Carpi in mind.⁷⁶ The mention of the Goths here also serves as a reminder that the subjugation of Dacia by this Germanic tribal confederation was nearing completion by the turn of the fourth century (as discussed in the previous chapter).

Other wartime events during the first tetrarchy are also hard to date. Sometime around 300, Constantius triumphed over the Alamanni at Lingones (the name of both a Gallic tribe and a city—present-day Langres in north-eastern France) and Vindonissa (modern-day Windisch in northern Switzerland). That is virtually all we know about the event (or, to be more precise, events, as the sites are nearly 300 km apart). We know neither whether these battles were part of a single campaign, nor the year in which they were fought. These battles were first mentioned by the panegyric of 310, which barely goes further than disclosing the names of the places, observing only that the emperor was wounded at Lingones and that many bones of the enemy forces who fell could still be seen at Vindonissa.⁷⁷ Eutropius offers a little more detail, saying that Constantius experienced defeat and tasted victory in a single day at Lingones. A surprise attack by the Alamanni forced the emperor to take refuge in the city, but since its gates had already been closed in defence against the approaching enemy, the locals hauled him over the walls by rope. Within five hours, a relief army had arrived at the city and, in the ensuing battle, “nearly 60,000 Alamanni” fell.⁷⁸ Echoes of this event can still be found in the works of later (sometimes much later) writers who agree on this ludicrous number of barbarian casualties and other details.⁷⁹ It is impossible to determine the exact year of these events; scholars usually date them to either the end of the third century or the first few years of the fourth century.⁸⁰ The same panegyric also mentions Constantius’ victory over “a great many Germani from various tribes” (immanem ex diversis Germanorum populis multitudinem) who crossed the frozen Rhine to some sort of island (insula)—this was the mouth of the Rhine and the Germani in question were apparently Franks – but were caught off-guard when the ice suddenly thawed, leaving them trapped, surrounded by the Roman fleet, and with no alternative but to surrender. Some the Romans allowed to return home, but others they took captive (and presumably absorbed them into the imperial forces).⁸¹

Prefects and Prefectures

One of the ways in which Diocletian changed the administration of the empire was that he splintered the power of the praetorian prefect. The gradual reform of this office then extended into Constantine’s time. In tandem with this, there was a progressive split in the military and civil administration of the empire, which again continued under Constantine’s solo reign.

From Augustus on, the office of praetorian prefect was undoubtedly second in importance only to the imperial title itself. Under the Principate, there tended to be two praetorian prefects; rarely was there only one prefect in office. They came from the equestrian order, but could be promoted to the senate while they were in office or afterwards; sometimes a praetorian prefect would be appointed consul. Their rank of vir eminentissimus was the highest within the equestrian order and was reserved for them alone.⁸² Besides commanding the praetorian guard, we have also seen how, in the third century, some of them led the army into war. In addition, they had many administrative responsibilities. We have also observed how prefects often sought to exert political influence. In 217, for example, one of them declared himself emperor. Sometimes, the praetorian guard even spun out of control, e.g. under Severus Alexander and in 238. That all ended with Diocletian—after Aper, never again did a praetorian prefect attempt a coup; they served their emperors with obedience. They continued to head the military and civil administration, taking care of tax collection and army supplies. They even wielded significant judicial powers (there was no appeal against their judgments) and sometimes helped the emperor to manage his military campaigns (e.g. Constantius’ invasion of Britain). As for the guard, its deployment in and around Rome had become an anachronism bereft of meaning, because Rome seldom saw an emperor at all from the late third century onwards. During the tetrarchy, some of the praetorian guard served in the East, where it was abolished by Galerius in 306. The praetorians were dealt their final blow by Constantine, who disbanded the guard in Rome in 312 after his victory over Maxentius. Even then, however, the office of prefect itself was not abolished. Instead, a greater emphasis was placed on its civil aspect. The prefect was close to the emperor and played the role of the empire’s chief bureaucrat. However, exactly when this office became purely civil is a problem addressed below.

The question of how many praetorian prefects the empire had at any one time during the tetrarchy has evolved. Timothy Barnes initially assumed that each of the four emperors of the first tetrarchy had his own prefect.⁸³ He later rejected this idea and concluded that, throughout the first tetrarchy, there had always been only a pair of prefects, each serving an augustus.⁸⁴ Even as the tetrarchy slowly disintegrated, each augustus (and each illegitimate augustus, such as Maxentius) had a praetorian prefect. Their number would thus change to reflect how many emperors the empire had.

As we have observed, Diocletian personally killed Numerian’s praetorian prefect Aper and retained Carinus’ praetorian prefect Aristobulus. We cannot say for sure how long Aristobulus served in this position, but by all accounts it was confined to the 280s, as he was made proconsul Africae in 290. We can assume that, from 286 at the latest (when Maximian was elevated to augustus), each of the two emperors had a praetorian prefect and his own units of praetorians.⁸⁵ One of the first praetorian prefects of the tetrarchy was undoubtedly Afranius Hannibalianus, who seems to have served Diocletian in the East sometime between 286 and 292.⁸⁶ He is paired with Julius Asclepiodotus, who, by analogy, must have been Maximian’s praetorian prefect for the West at this time.⁸⁷ These two are twinned in three places: first, in an inscription (ILS 8929); next, the author of the HA mentions them along with Diocletian, Carus, and Constantius in a sort of list of generals who, as “very famous commanders” (praeclarissimi duces), came “from the school of Probus” (ex eius disciplina)⁸⁸; and, finally, they were consuls together in 292. Tellingly, Hannibalianus, as Diocletian’s prefect, was consul prior, while his colleague Asclepiodotus had a slightly less honourable place in the consulship (consul posterior).

Sometime around 296, Hannibalianus was replaced in the East by the jurist Aurelius Hermogenianus (Hermogenian), while Asclepiodotus remained in his post until at least 296 and took part in Constantius’ campaign against the usurper Allectus in that year.⁸⁹ Barnes initially “assigned” Asclepiodotus only the period between 285 and 292, believing that the praetorian prefecture in the West, specifically between 288 and 293, was also held by the later tetrarch Constantius. However, since a prefect named Asclepiodotus is attested for 296 as well, Barnes speculated that there were two praetorian prefects of the same name in the empire in the 290s, and that the second may, for example, have been the son of the first. Barnes later changed his mind and recognised that one and the same Asclepiodotus held the office from at least 292 and at least until 296; logically, then, Constantius could not have been praetorian prefect before he became caesar.⁹⁰

Before being appointed as Diocletian’s praetorian prefect, Hermogenian was his magister libellorum. It was in this capacity that, in 295, he produced a small collection of laws dealing mainly with private law. Known as the Codex Hermogenianus, it consisted mainly of imperial rescripts from 293 to 294. It has not survived. The Codex Gregorianus—likewise no longer extant—is similar. We do not even know the name of the jurist who compiled this work (Gregorius or Gregorianus?). Whoever he was, around 292 he put together a collection of imperial laws issued in the period from the time of Hadrian until 291. To deduce the focus, scope, and purpose of these two codes, we must lean on the much later Codex Justinianus, which drew on them for inspiration. Both works were updated at least once; the Codex Hermogenianus was slightly shorter than the Codex Gregorianus.⁹¹

The few other surviving names of the first tetrarchy’s praetorian prefects are difficult to place in time or even in office, i.e. it is not easy to determine when and which augustus they served. The problem is compounded by the fact that some of them are identified in our sources only by the term praefectus (or its Greek equivalent), so we cannot be sure whether they were indeed praetorian prefects.⁹² Sometimes even the historicity of a particular figure may be questionable. Take one Verconnius Herennianus. The only mention of him is in the Historia Augusta, where he actually crops up in two different biographies. The biography of Probus has already been quoted here; in that passage, Herennianus is mentioned as one of the commanders who came from “the school of Probus”, along with Diocletian, Carus, Constantius, Hannibalianus, and Asclepiodotus. In Aurelian’s biography he is identified directly as Diocletian’s praetorian prefect and is again mentioned in connection with Asclepiodotus.⁹³ This link and the references in the two different biographies of the Historia Augusta—notwithstanding the fact that the HA is most likely the work of a single author, and even though Herennianus is not mentioned elsewhere—suggest that he genuinely existed; Verconnius Herennianus could have been Diocletian’s prefect in the late 290s, for example.⁹⁴ We will revisit the evolution of the post-Diocletian praetorian prefecture later.

The prefecture of the city of Rome and the consulship were, and under the tetrarchy remained, highly prestigious positions within the imperial hierarchy. However, as far as the consulship was concerned, the year 288 marked the end of the tradition where emperors and prominent members of the senate shared consular authority. Until then, this was a quite common practice in the third century.⁹⁵ After 288, the consulship was held either just by a pair of emperors (the two augusti, the two caesares, or one augustus and one caesar) or just by senators (often praetorian prefects who had been elevated to the senate).⁹⁶ In other words, at no time after this did the tetrarchs or Constantine or his sons have any need to raise to the consulship someone who was not an emperor or a member of the imperial family. When Ammianus Marcellinus later wrote that, before 363, the last time anyone who was neither emperor nor a member of the imperial family had been co-consul with the emperor was in 285, he was only slightly wrong.⁹⁷ In this respect, Ammianus specifically names Aristobulus, whom we learn served as both praetorian prefect and co-consul in 285 under Carinus, with Diocletian then not only confirming him as praetorian prefect but also retaining him as consul for the rest of 285. Not to mention the fact that Aristobulus later became urban prefect of Rome. Ammianus forgot (or did not know) that the emperor Maximian’s co-consul in 288 had been a certain Pomponius Ianuarianus, whose career followed a similar trajectory to that of Aristobulus: he was governor in Egypt in 284, but joined Diocletian; he was a mere eques; and Diocletian rewarded him with membership of the senate, a consulship, and immediately afterwards an urban prefecture (288–289).⁹⁸

In the Notitia Dignitatum, an anonymous register of dignitaries in the Roman Empire, the urban prefect of Rome (praefectus urbis or praefectus urbi) ranked just behind the praetorian prefects in prestige.⁹⁹ The term of office is attested to have ranged from one month to four years between 284 and 337,¹⁰⁰ but on average urban prefects were in office for only a year and a few months, as there were 39 prefects (some of whom held the prefecture twice) during that period. Twenty-one of them became consuls during their career and, as we have seen, some were also praetorian prefects.¹⁰¹ After Gallienus’ reforms deprived the senatorial class of its dominant position in provincial administration, the urban prefecture evidently became the most important office a senator could hold. The power of the urban prefect increased further once Rome ceased to be an imperial residence. The urban prefect controlled Rome and its environs and, like the praetorian prefect, was considered the emperor’s representative in the exercise of judicial powers since, like the praetorian prefects, there was no appeal against his judgments.¹⁰²

Provinces and Dioceses

In the previous chapter, we traced how imperial administration was reformed under Gallienus. Diocletian used that reform as a solid foundation on which to build. In particular, he greatly increased the number of provinces by fragmenting the existing provinces into smaller units.¹⁰³ This had been done before, but under Diocletian we saw a change that was as massive as it was rapid, since the number of provinces doubled (from 48 to 98).¹⁰⁴ It is commonly held that Diocletian took this action because he wanted to gain better control over the provinces’ financial administration, judiciary, and public policy, and specifically over municipal government bodies—the local senates or curiae, which were primarily responsible for tax collection.¹⁰⁵ This new type of province probably began to emerge in 293.¹⁰⁶ At the same time or a little later, the newly created provinces were clustered into groups known as dioceses, headed by an official called a vicarius. The dioceses were probably a response to the fact that the sudden increase in the number of provinces was too much for the praetorian prefects to handle.¹⁰⁷ The vicarii were officials (literally, “substitutes”) “acting on behalf of praetorian prefects” (agentes vicem praefectorum praetorio). As they also held judicial powers, they could hear appeals against decisions made by the provincial governor. Twelve dioceses were established. According to the anonymous “Verona List” (Laterculus Veronensis) of provinces and dioceses, probably drawn up around 314 and preserved in a 7th-century manuscript, Diocletian created the following dioceses (the number of provinces in the diocese is given in parentheses): Oriens (15), Pontica (7), Asiana (8), Thracia (6), Moesiae (11), Pannoniae (7), Britanniae (4), Galliae (8), Viennensis (7), Italia (12), Hispaniae (6), Africa (7) (Map 4.1).¹⁰⁸

Map 4.1

(Source Ancient World Mapping Center © 2020 [awmc.unc.edu]. Used by permission)

Map of the Roman Empire’s dioceses following Diocletian’s administrative reforms at the end of the third century.

Pannonia is an example of a newly organised region. The original two provinces of Upper and Lower Pannonia (Pannonia Superior, Pannonia Inferior) were divided into four after Diocletian’s reform. Both original names were retained, with Savensis being hived off from the former, and Valeria (which Diocletian named after his daughter) from the latter.¹⁰⁹ These four provinces were joined by Noricum, now divided into two provinces (Noricum Ripense and Noricum Mediterraneum), and, with the addition of Dalmatia, the Pannonian diocese was born.

The division between senatorial and imperial provinces disappeared. To be sure, the provinces of Africa and Asia continued to be administered by senatorial governors carrying the grand title of proconsul, who were directly responsible to the emperor,¹¹⁰ but their territory was now much smaller. The emperor alone appointed governors for all the provinces, and even the urban prefect in Rome.¹¹¹ Italy (Italia) was divested of its special status and became a twelve-province diocese which, unusually, had two vicarii. These provinces were headed by governors called correctores, who were mostly from the senatorial class.¹¹² The bulk of the governors of the provinces outside Italy, on the other hand, came from the equestrian order (as a continuation of the trend started in Gallienus’ time).¹¹³ Most of them held the lower title of praeses, first encountered during Gallienus’ reign, and the rest bore the higher title of corrector.¹¹⁴ Egypt (Aegyptus) was also reduced to an ordinary province and split in two: in the 290s, its southern half became the province of Thebais, governed by a praeses; Egypt proper was managed by an official who kept the title of praefectus Aegypti.¹¹⁵

All these measures were restricted to civil administration; Diocletian organised the defence of the empire separately. The administrative reform saw provincial governors stripped of all military power, leaving them responsible solely for collecting taxes and exercising judicial power. The same applied to those in charge of the dioceses. Legates disappeared and military authority was assigned to military commanders called duces. Which brings us to the reform of the army.

Diocletian’s Army

The army that Diocletian took over in 284 was born of the emperor Gallienus’ reforms. Diocletian built on his predecessor’s work by introducing military reforms of his own. Diocletian, who probably entered the military in the final years of Gallienus’ reign, was a product typical of that emperor’s reforms, which gave men of humble birth, such as himself, a shot at commanding the army. The tetrarchy persevered with this trend; indeed, as we have seen, at least two of Diocletian’s colleagues (Maximian and Galerius) were very low-born.

We can be sure that Diocletian made moves to divide the army between himself and his co-ruler Maximian; once the caesares were appointed, they too acquired armies of their own. Diocletian was also constantly strengthening these armies: besides maintaining the existing legions, he gradually created many new units. He placed an emphasis on the cavalry and a strong central reserve (or, more precisely, reserves), both of which were foreshadowed by Gallienus’ creation of an elite cavalry corps permanently stationed at Milan.¹¹⁶ Although we find no mention of these equites of Gallienus (and also of Claudius and Aurelian) during Diocletian’s reign, and although this corps was probably not a direct forerunner of the mobile armies we know from the tetrarchs’ time, they unquestionably reflected the general trend towards building up mobile units and, especially, the cavalry as the Roman army’s main strike force.

We have seen that Diocletian and Maximian initially engaged in rather modest and defensive warfare. The first indication we have that the empire had enough forces for a limited offensive was the joint strike against the Alamanni in 288, but even then Diocletian and Maximian had to combine their elite escorts to achieve their planned operational objectives. By 296, however, the empire had raised the forces required for three major and almost simultaneous offensive actions: Britain was reconquered by Constantius, and a year later Galerius was at war with the Persians while Diocletian was suppressing a revolt in Egypt. The imperial forces had grown. That was beyond question. But by how much?

The number of soldiers this new army had is discussed in detail in Appendix C; at this point, it is sufficient to note Lactantius’ observation that Diocletian, by appointing three more emperors, “divided the world into four parts” and created three more armies, and that each of the tetrarchs now aspired to a “much larger” army than the emperors before Diocletian had had.¹¹⁷ Lactantius’ assertion that there were four times as many troops under Diocletian is obviously preposterous and, in all likelihood, merely echoes the fact that each of the tetrarchs had his own army. If some 350,000 men served in the armed forces of the late Principate, and the maximum strength of the Roman army under Diocletian was around 450,000 men (see Appendix C), this translates into an increase not of 300%, as Lactantius claims, but of 30%. What is more, this increase undoubtedly took place over a period of many years. To make this uptrend sustainable, individual towns were responsible for conscripting local men, and the sons of veterans were encouraged to join the army.¹¹⁸

As we have already mentioned, the officers Diocletian placed in command of military units in the provinces were known as duces. The region under their command did not always coincide with the boundaries of the provinces; some of them commanded units in several provinces at once. For example, Egypt, although divided into different provinces, still had a single military commander (dux) who was charged with the defence of both Egypt and Thebais, as well as the two Libyas.¹¹⁹ Although the military commander and the civilian governor were each responsible for their own duties and tasks, there were naturally some areas (such as keeping the army supplied) in which they worked together. Significantly, the duces were still accountable to the praetorian prefects during the reign of Diocletian.¹²⁰

It is not clear whether the division of the Roman army into mobile (comitatenses) and frontier (limitanei or ripenses) units was the work of Diocletian or Constantine. This division is not mentioned until the second half of Constantine’s reign.¹²¹ The key account here is provided by Zosimus, who praises Diocletian for leaving all his troops at the frontier to put an immediate stop to barbarian incursions there, but chides Constantine for pulling most of his troops inland.¹²² If Zosimus is right, this begs the question as to when Constantine decided to create such a mobile army. Some have suggested that the most opportune time may have been after the Battle of the Mulvian Bridge (see Chapter 7).¹²³ It could just as well be argued that Constantine and Licinius would hardly have been capable of working together on such a large-scale project as the systemic reorganisation of the army. With this in mind, David Potter is more inclined to the view that the comitatenses had already been created by Diocletian¹²⁴; Hugh Elton, for the same reason, concludes that it was actually Constantine who created the mobile army after his final victory over Licinius in 324.¹²⁵ Brian Campbell stresses the continuity underlying the development of the army and is reluctant to attribute the creation of the mobile corps to either of these emperors. In his opinion, mobile troops already existed by the time of the first tetrarchy, but they did not yet play as significant a role in the defence of the empire as they did later under Constantine.¹²⁶ Indeed, inscriptions and papyri attest that Diocletian and the other tetrarchs each had some sort of “field army” to accompany them (accordingly called the comitatus or “retinue”), which was considerably larger than the guard corps of protectores.¹²⁷ It was this continuity in the army’s evolution from Gallienus to Constantine (combined with an absence of sources reporting on how it developed) that prevents us from determining when the mobile army came into being. We therefore have no exact year for the formation of the mobile army.

The consensus, however, is that it was Constantine—evidently towards the end of his reign—who created the command positions of magister peditum (general of the infantry) and magister equitum (general of the cavalry).¹²⁸ These generals commanded the comitatenses and, indirectly, troops in the provinces, since the duces were subordinate to them.¹²⁹ When the praetorian prefects were deprived of all their military powers, this not only provided the final link in the chain of military command, but also completed the process of separating the military and civilian spheres in the administration of the empire.¹³⁰ Even the new palace guard (scholae palatinae), which was probably not created until Constantine’s reign, answered to a different official.¹³¹

Diocletian’s defensive policy was conservative and rested on three pillars: increasing the number of troops; firmly securing the borders; and engaging in occasional offensives when the circumstances allowed. The cumulative effect of the Diocletian and Constantinian reforms would give rise to a new type of army that survived in the West until the end of the Western Roman Empire and in the East for a little longer.

Diocletian’s Monetary, Price, and Tax Reforms

Diocletian’s monetary reform, initiated in 294, built on the reform introduced by Aurelian (see Chapter 3). It was evidently prompted by the need to take care of a growing army; indeed, the same can be said of Diocletian’s interest in keeping prices at an acceptable level and, above all, of his new tax collection system.¹³² These three reforms must therefore be viewed as a comprehensive effort by Diocletian to address the major concern of how to cover spending under the state budget, especially the needs of the army.¹³³

As to currency, the circulation system was stilled topped off by the gold aureus, which weighed only slightly less than in Aurelian’s time (about 5.3 g versus 6.45 g).¹³⁴ As mentioned elsewhere, aurei (and gold in general in the empire) had always been more of a “gift metal”, i.e. they were not suitable for normal financial transactions and did not form the basis of the circulation system.

The newly introduced silver argenteus was consistent with the original silver denarii of the early empire, specifically from the time of the emperor Nero, in both its weight (about 3.4 g) and high purity. This was quite extraordinary considering the lamentable fate of the devalued pseudo-silver currency we saw in the third century.¹³⁵ We have no idea what prompted Diocletian, apart perhaps from nostalgia for the days of his early empire, to put a virtually pure-silver coin into circulation.¹³⁶ When, 20 yearsbefore Diocletian, Aurelian decided to increase the silver content of antoniniani from 2% to about 5%, this was a much more modest but also significantly more effective move. The reaction to Diocletian’s argentei was entirely predictable: people immediately started hoarding these almost pure-silver coins. The fact that the argenteus was only minted in small batches and only by certain mints (which is why it is rarely found today) meant that, even if it had remained in circulation, it would have had no major impact. To top it all off, Diocletian valued his argenteus at just 50 old debased denarii (the emperor later felt compelled to correct this mistake; see below). The old denarii (called denarii communes, or dc, by modern writers), despite no longer being minted or circulated, were still used to calculate prices and wages.

At the heart of Diocletian’s currency reform was the nummus (literally “coin”),¹³⁷ a silver-washed bronze coin weighing about 10 g and containing 4% silver; it essentially played the role of the old aurelianus, which was no longer minted but remained in circulation. Here, too, Diocletian was emulating Nero: while the argenteus was intended to take over the role of the former (very pure) denarius, his nummus was supposed to become the new sestertius; and just as 1 denarius had been worth 4 sestertii, so 1 argenteus was worth 4 nummi. However, this system did not work as planned; as Antony Kropff points out, who would buy a product worth 4 nummi for 1 argenteus (assuming they could get their hands on one in the first place)? No one in possession of such a valuable coin would simply give it up when they could pay the same price with four less valuable coins.¹³⁸

“New aureliani”, weighing about 3g and containing no silver, as they were made of copper, were also minted. These were radiate coins (so-called because of the rayed-crown worn by the emperor on the obverse). Finally, copper “new denarii”, weighing 1.3 g and again silverless, were struck.¹³⁹ These were laureate coins, named after the laurel wreath the emperor is depicted as wearing.¹⁴⁰ They were minted only in small numbers in the West and hardly at all in the East.¹⁴¹

As with Aurelian’s reform, we are left to conjecture the relative values of these coins. Various suggestions have been made. According to one proposal, in 300 the values were as follows: 1 aureus = 20 argentei = 80 nummi = 1000 dc.¹⁴² If we add all the other types of coins, we arrive at the following ratios: 1 aureus = 20 argentei = 80 nummi = 250 “new aureliani” = 500 “new denarii” = 1000 dc.¹⁴³ Obviously, this is only a theoretical equation. The problem is that not all of the coins described were actually in circulation. The aureus, rather than a coin in circulation, appears to have functioned as a store of value.¹⁴⁴ The relatively high-value argenteus, as we have seen, was rarely found in circulation as people were quick to hoard it. To all intents and purposes, only the ‘‘new aureliani’’ (which, in accordance with Gresham’s law, seem to have rapidly displaced the more valuable old aureliani) and, of course, the nummi were circulated in sufficient quantities. The “new denarii” were dogged by a different problem: inflation had rendered them all but worthless. Soon after Diocletian’s abdication (305) they and the “new aureliani” ceased to be minted.¹⁴⁵

The currency reform of 294 was therefore evidently only moderately successful at best. The main drawbacks were the excessive purity of the argenteus and the fact that the nummus and, especially, the argenteus were undervalued. As a result, an edict usually referred to as the Currency Edict was promulgated on 1 September 301. Also known as the Aphrodisias Edict after the city in Caria, Asia Minor, where an (incomplete) copy was found, it doubled the value of these very coins: the argenteus was to be worth not 50 dc, but 100 dc, and the nummus was to be worth 25 dc instead of the previous 12.5 dc. The other coins were to retain their value. This means the following ratios applied: 1 aureus = 10 argentei = 40 nummi = 250 “new aureliani” = 500 “new denarii” = 1000 dc.

Between 20 November and 9 December 301,¹⁴⁶ the tetrarchs issued the much more famous Edict on Maximum Prices,¹⁴⁷ which primarily sought to combat ever-spiralling inflation (by setting a ceiling on the prices of approximately 1500 products, raw materials, animals, slaves, and services). The text of the edict indicates that it was intended to apply throughout the empire, but the inscriptions in which the edict is preserved come almost without exception from a handful of Eastern provinces.¹⁴⁸ The prices thus dictated by the government to the population and applicable everywhere in the empire without distinction were set in old denarii, which were no longer in circulation. The text itself is very interesting and of immeasurable value to us. No other official, private, or literary text of the ancient world provides such an extensive list of goods and prices.¹⁴⁹ The general consensus today is that this edict was unsuccessful. One scholar had no qualms about calling it “an act of economic lunacy”.¹⁵⁰ In Diocletian’s defence, neither he nor anyone else in antiquity was an economist.¹⁵¹ Nevertheless, the edict refuses to grasp that prices depend on demand for goods and various other factors, such as the price of transportation. Instead, it speaks emotively of the avarice of merchants who artificially drive up prices, thereby sopping up wretched soldiers’ entire salaries which the whole empire has paid for through taxes.¹⁵²

Lactantius, observing the effect that the edict had on the local population in Nicomedia, noted that people were executed for even minor offences, that merchants did not dare sell their goods out of fear, and that prices rose even more. The law was then apparently revoked.¹⁵³ Interestingly, Lactantius says that Diocletian himself, by perpetrating “various injustices” (variis iniquitatibus), fuelled the very surge in prices he was trying to contain. Lactantius names them: extensive building, the proliferation of soldiers and provincial officials, plus an increased number of imperial residences and the high cost of relocating the imperial court from one place to another. Apart from Lactantius (and papyri from Egypt), no other source mentions what impact the edict had, and frankly we do not know how long the edict was in force. Although prices did indeed rise in the next decade, the edict was probably more effective and longer lasting than Lactantius’ account suggests.¹⁵⁴

Besides the prices of goods and services, the Edict on Maximum Prices also affected the value of coins. The price of a pound of gold was set at 72,000 dc (and the price of a pound of silver at 6000 dc, meaning that the gold-to-silver ratio was still 1:12). However, the fact that it took one pound of gold to mint sixty of Diocletian’s aurei meant that the aureus was now worth 1200 dc. As we have seen, the Currency Edict decreed that 1 argenteus should be equal to 100 dc and 1 nummus should be equal to 25 dc. Assuming that the two edicts were complementary rather than contradictory, the equation is simple to work out: 1 aureus = 12 argentei = 48 nummi = 1200 dc. Most numismatists work on the basis that 1 “new” (and usually also old) aurelianus was worth 4 dc. This would give us: 1 aureus = 12 argentei = 48 nummi = 300 “new” or old aureliani = 1200 dc.¹⁵⁵ The “new denarii” had no impact and can be ignored here (their likely value was 1 or 2 dc). Kropff elegantly simplifies the whole problem even further by claiming that all other coins not circulating in the system can be disregarded. Once aurei are also removed from the equation, we get: 1 argenteus = 4 nummi = 25 “new” or old aureliani = 100 dc. If we also remove the rare argenteus and the non-existent dc, we arrive at this simple equation: 1 nummus = 6.25 “new” or old aureliani. And that is virtually all that remained of Diocletian’s monetary reform after 301.¹⁵⁶

If aurei and argentei were all but out of circulation in the system, larger financial transactions had to be made in the coin of nearest denomination, which was the nummus. It was evidently common practice to package nummi in sealed bags containing a set number of coins. We know of these bags from contemporary depictions, which also indicate their value. With a standard value of probably 12,500 dc, they would not have been easy to carry around.¹⁵⁷ In other words, prior to the Currency Edict, they contained 1000 nummi and weighed 10kg, but after the reform they contained only 500 nummi, i.e. 5kg of metal. Made of leather, these pouches were called folles; later, the coins which were measured by such bags also came to be known by this name. This was plainly a stopgap measure that was unsustainable in the long term, as Constantine decided to start reducing the weight of the nummus from 307. Besides, Constantine would come to have his own ideas on how to reform the currency in circulation (see Chapter 10).

Most freshly struck coins were destined for the army. Although soldiers were mainly paid in kind during the tetrarchy (see below), they did also receive money: stipendia (which can be translated as “salaries”) and donativa (a kind of “bonus”). Under Diocletian, stipendia were paid three times a year (in January, May, and September), but inflation rendered their value negligible, so they were essentially only a token gesture. It was the donativa that carried actual real value; emperors paid these to soldiers upon accession and on politically significant occasions, whether regular, such as on the anniversary of when they assumed power (dies imperii) and on their birthday (dies natalis), or irregular, such as before a major military campaign or when the emperor held a consulship. The purpose of the donativa was to reinforce the bond between the army and the emperor.¹⁵⁸

In the third century, emperors felt the need to decentralise coin production, primarily so that money could be distributed more quickly to military units, but also because barbarian invasions and internal wars were a threat to communications. Consequently, there was a rise in the number of state mints within the empire in that century. From 239 onwards, state coins were minted not only in Rome, but also in Viminacium on the Danube; by the time of Valerian and Gallienus, there were six mints in the empire, and under Aurelian there were eight.¹⁵⁹ Parallel to this, there was still local coinage in the Roman East: in the middle of the third century, about a hundred cities in Asia Minor, the Balkans, and Syria were still minting their own bronze and silver coins. In this respect, Egypt had enjoyed a special status from the very dawn of imperial rule. Since the reign of Tiberius, silver tetradrachms, worth a denarius, had been minted in Alexandria with the permission of the emperors and under the supervision of the state, but they were valid only in Egypt and were exchanged for denarii upon departure from the province. Just as the denarius declined in the third century, so did the weight and purity of the tetradrachm. In the wake of Diocletian’s monetary reform, the Alexandrian mint stopped coining tetradrachms in 296 and became part of the unified system of state mints. All other local Greek minting in the East ceased at this time; the language of coins was now Latin alone and the coinage system in the empire had become completely uniform. Even so, the number of state mints continued to grow. By the time control over Britain was restored in 296, there were fourteen state mints working for the tetrarchs.¹⁶⁰ Yet, the currency in circulation in the West was not entirely to Diocletian’s liking. As we saw in the previous chapter, after the annexation of the “Gallic Empire” by Aurelian, the very debased coinage of Tetricus and even older coins remained in circulation here alongside Diocletian’s nummi for a long time (into the first decades of the fourth century).¹⁶¹

As already mentioned, the increasing number of soldiers in Diocletian’s army burdened the state with rising costs. In connection with the collapse of silver currency, which we discussed in the previous chapter, during the third century the Roman state began to levy taxes in kind, since taxes paid in money would have been almost worthless. People were placing little faith in the value of money, but a state that was constantly debasing its coinage had even less confidence in it! These in-kind taxes, called annona militaris or simply annona, constituted the main element of soldiers’ pay and were the principal direct tax imposed on the population.¹⁶² By eliminating the need to collect taxes (and pay its employees) in money, the state neatly sidestepped the problems of currency devaluation and price increases without being forced to address them. In terms of supplying the army—which, after all, was the main purpose of taxation in the late Roman Empire—this was not even necessary. Instead, each year the government imposed on curiales (the members of city councils) the obligation to collect in-kind taxes and made the m liable—on behalf of the entire city and its surroundings—for delivering that fiscal year’s taxes.¹⁶³

To keep the wheels of Diocletian’s growing army of soldiers and bureaucrats turning, tax collection had to be as efficient as possible and the tax burden had to be spread as fairly as possible over the whole empire. Nevertheless, taxpayers in some provinces were clearly shouldering too much of the burden while others elsewhere paid little; the general unfairness of the earlier system was noted by the Egyptian prefect Aristius Optatus in 297 when he promulgated Diocletian’s tax reform in his province by edict. As Potter observes, the Egyptians—who until then had paid relatively low taxes—let their feelings be known almost immediately when Domitius Domitianus revolted against the government (as discussed above).¹⁶⁴

Diocletian was aware, however, that some of the population could afford to pay more than others, depending on their wealth, so it would not make sense to tax everyone equally. Another factor that clearly had to be considered was that land in some parts was more fertile than in others. Also, because of inflation, it was impossible to set a fixed monetary value on land in a situation where the real value of money was declining. Diocletian therefore did two things: first, he made in-kind tax a standard tax liability; secondly, he built the system of taxation for the whole empire on entirely new foundations. We do not know exactly when this happened,¹⁶⁵ but a tax calculation system based on a land-based unit called the iugum and a per-head unit of measurement known as the caput appears to have been gradually introduced in the empire from the early 290s. The iugum always had approximately the same value, but it was not a consistent measure of land, as this varied according to the type of land and the crops grown: a smaller area of prime land could correspond to a larger area of poorer-quality land, for example. Creating this system (known as iugatio) and putting it into operation must have been a gargantuan task. Tax assessors (censitores) visited every village in the area where the census was being undertaken. Here, they estimated the yield derived not only from arable land, but also from pastures, vineyards, olive orchards, and other agricultural areas. The second tax calculation system, capitatio, was just as complicated. Nominally, its unit of measurement, the caput, was equal to one farmer, but in some places women would be counted as one caput (e.g. in Syria), in others they were deemed to be half a caput (in Asia Minor), and in Egypt they were ignored entirely. Another variation within the system was the age at which the population was taxed (it seems that people were usually considered liable for tax between the ages of 14 and 65). Livestock were counted as fractions of a caput. The total tax to be levied was reached by aggregating the total juga and capita (the two units carried the same value in these calculations). The censitores then entered this amount in registers that were passed on to local municipal councils as the bodies responsible for collecting taxes. This combined taxation (jugatio et capitatio) was levied on the rural population; the taxes do not appear to have been exacted from the urban population (via capitatio) until the end of Diocletian’s reign. This mixed method of calculating taxes depended on accurate property assessments conducted every five years. Under Diocletian, iugatio was paid in kind, while capitatio was paid in money, although here again there were regional variations.¹⁶⁶ The in-kind annona thus persisted to some degree, but money payments were exacted alongside it now that the monetary system had been at least partially rehabilitated. It should also be noted that the system described above was by no means uniform and varied from one part of the empire to another by reflecting local traditions.¹⁶⁷

Under this system, large families with small farms were arguably subject to more tax than landowners with large plots and many tenants (coloni), who paid their own capitatio. As A. H. M. Jones reminds us, this is always inevitable when both land and people are taxed, and there is no reason to suppose that the system was felt to be unjust.¹⁶⁸ Taxes were at least regular in the time of the tetrarchy, and the government could, and did, grant concessions, for example, by reducing the value of a caput in a particular area from one man to two or more, by simply cutting a certain number of capita for a given town or area, or by retrospectively forgiving arrears. Diocletian’s new tax system was not only efficient, but also tried to be fair. Although we have little information about Diocletian’s life before 284, this extraordinary emperor seems to have been of very low birth, coming from the family of a “scribe” who worked for a certain senator (see Chapter 3). Diocletian’s military service undoubtedly convinced him that the state needed to have a strong army that was well supplied and well paid. Likewise, if his father was engaged, perhaps, in bookkeeping on the senator’s lands in Dalmatia, his childhood experience may have taught him the need for the tax burden to be distributed fairly; for that matter, the main purpose of taxation was to keep the army machine well oiled. We also know that Galerius, whom Diocletian chose as his closest collaborator and his successor in the East, was of peasant origin. Had he done nothing else, Diocletian’s tax reform would have made him one of the greatest figures of the Roman Empire. His was the first major change to the Roman tax system since the reign of the emperor Augustus, and it remained in force, with variations, until the seventh century.¹⁶⁹

It remains to describe two other taxes that had already embedded themselves by Diocletian’s time. The aurum coronarium was the gift of a golden crown or wreath made to the emperor on his accession and every five years thereafter. As this tax was paid by the cities, responsibility for it fell primarily on the curiales. The aurum oblaticium was a similar tax paid by the senate. Since it took the form of pure gold, the value of this tax was not eroded by inflation. In the third century, it was practically the only way the government extracted gold from the people of the empire.¹⁷⁰

As we have already mentioned, Diocletian deprived Italy of its special status so that it was administered like any other province. This included subjecting Italy to taxation (until then there had been no direct taxes here).¹⁷¹ However, Rome itself—including a 100-mile radius around the city—remained exempt from this obligation.¹⁷²

The Persecution of Christians During the First Tetrarchy

Although they did not consider themselves deities, Diocletian and his colleagues in the tetrarchy were deeply wedded to the world of the gods. We have seen how they forged links with Jupiter and Hercules by giving themselves the names Jovius and Herculius. We can also distinguish how they laid claim to other aspects of divine veneration. Instead of the simple greeting (salutatio) given to previous emperors, kneeling and kissing the hem of the emperor’s robe (adoratio) were now required.¹⁷³ Aurelius Victor also later claimed that Diocletian was the first emperor since Caligula and Domitian to have himself publicly addressed as “lord”, called a deity, and venerated as a god (adorari se appellarique uti deum).¹⁷⁴ To be sure, Caligula did indeed claim divine honours, and the full title dominus et deus (lord and god) first appears under Domitian, but the emperor Commodus also regarded himself as a god, and various emperors of the Principate period were addressed by the term “lord” (see Chapter 3). Most importantly, the introduction of the title dominus et deus in the third century was not Diocletian’s idea: it had also been used by his predecessors Aurelian (at least on coins), Probus, and Carus.¹⁷⁵ In other words, by making this demand, Diocletian was simply falling into line with a deep-seated trend. Diocletian himself was clearly a very pious man. A number of coins survive on which he and the other tetrarchs are depicted making sacrifices.¹⁷⁶ Bill Leadbetter recalls that the complex built to house Diocletian’s “retirement” palace in Split included four temples; if Diocletian’s faith had been skin-deep, surely one would have sufficed.¹⁷⁷

There was a long period during which Diocletian seemed not to mind Christians and pursued a positive religious policy that promoted traditional deities and effectively tolerated all cults. This tolerance had existed in the empire since 260, when Gallienus ended Valerian’s persecution of Christians. In all this time, emperors and provincial governors alike essentially turned a blind eye to the fact that Christianity remained illegal.¹⁷⁸ As its numbers of followers grew, it became harder to ignore; in Nicomedia itself, where Diocletian resided for most of 303–305, a church was visible from the imperial palace. But Christianity and Diocletian’s ideology were on a collision course. It was only a matter of time before the conservative Diocletian, who cherished tradition when it came to beliefs, would conclude that a religion which refused to conform posed a danger to the state. By the end of the thirdcentury, Diocletian had succeeded not only in securing the borders and establishing complete political control over the empire, but also in reorganising its civil and military administration and reforming the tax system and currency. In all of these activities, he was driven by a desire for unity, and the same can be said of his attitude towards Christianity. Like Decius and Valerian, he believed that religious conformity was essential in the empire if the favour of the gods was to be maintained. His 295 law against incest, the brief text of which is documented in the Codex Justinianus,¹⁷⁹ is often mentioned in this context.¹⁸⁰ The law itself is not of interest, but it was originally accompanied by a preamble that has been preserved in the late-4th-century Collatio legum Mosaicarum et Romanarum. Among other things, that preface observes: “There can be no doubt that if we see all the inhabitants of our empire leading a proper, pious, peaceful and chaste life in every respect, even the immortal gods themselves will remain favourable and conciliatory towards the Roman state, as they have always been”.¹⁸¹ The devout monarch, who considered himself the father of all his subjects,¹⁸² felt ever more urgently that it was his duty to ensure that there was universal respect for the gods. Yet, the question remains as to why Diocletian did not resort to repression until 303. Stephenson interprets this simply as meaning that it was only after Diocletian had defeated Persia and introduced his reforms that he no longer had any serious enemy or major problem to contend with, and so he could begin his attempt to restore the “moral and spiritual health” of the empire and make “a fictive return to traditional Roman values”.¹⁸³ The fact that, relatively speaking, the empire’s largest concentration of Christians was in the East (especially in Asia Minor, Egypt, and Syro-Palestine) certainly played a role, and it was in these regions that we tend to find Diocletian in 296–305 (as we saw above, until then he had been focusing more on the Danube frontier).

The purge of the army that Diocletian ordered, probably as early as 297, in the context of the war with Persia and the revolt in Egypt acted as a sort of prelude to this persecution. The empire, experiencing an unexpected crisis, needed the support of the gods more than ever.¹⁸⁴ Lactantius explains that once, when a sacrifice had failed repeatedly, the priests were confused and ascribed it to the presence of unbelievers, i.e. Christians. Diocletian immediately ordered that everyone in the palace take an active part in the sacrifice or be scourged. Subsequently, all soldiers throughout the empire were obliged to participate in the sacrifice, and those who did not obey were dismissed from the army.¹⁸⁵ The persecution of the adherents of Manichaeism in 302, on the other hand, was largely politically motivated, as Manicheans were thought to sympathise with Persia.¹⁸⁶

Diocletian spent the turn of 303 in Nicomedia with his caesar Galerius. According to Lactantius, they held one-on-one talks, spending the whole winter conferring whether or not to start persecuting Christians, with Galerius reportedly in favour of taking a hard line and Diocletian opposed.¹⁸⁷ Galerius’ role in the Great Persecution is difficult to gauge. Lactantius portrays Galerius as a conniving, evil, brutal man to whom Diocletian slowly but surely submitted, eventually bending to his will.¹⁸⁸ And yet the final decision unquestionably lay with Diocletian. He went on to consult Apollo’s oracle in Didyma (near Miletus in Asia Minor)¹⁸⁹ before finally giving his orders.

Early in the morning of 23 February 303, soldiers went to the church in Nicomedia and razed it to the ground.¹⁹⁰ The next day, the first edict against Christians was issued, resulting in the demolition of churches, the burning of Christian books, and the confiscation of property.¹⁹¹ The Christians, however, made do without churches, since the bishops were able to organise meetings and common prayer in the open air. This prompted a second edict, promulgated in the spring or summer of the same year, ordering the arrest of all bishops, though it does not seem to have applied to the West.¹⁹² Prisons in the Roman world were places where the accused awaited trial or sentencing; they were not intended for long-term confinement, and their limited capacity was probably insufficient for the sudden influx of many prisoners.¹⁹³ Consequently, later on in 303, a third edict was issued allowing those bishops who made sacrifices to be released. This edict, too, seems to have applied only to the East. Early in 304, there was a fourth edict ordering all of the empire’s inhabitants, on pain of execution, to make sacrifices to the gods. As in the case of Decius’ edict (see Chapter 3), many Christians presumably somehow avoided performing the sacrifice. Furthermore, despite the empire-wide nature of this edict, it was most likely not applied in practice in the West (and if it was, certainly not systematically).¹⁹⁴ The two Western tetrarchs took quite different stances: while Maximian tried hard to apply Diocletian’s first edict within his sphere of power, and we know that executions went ahead in Africa, his caesar Constantius appears to have seen no reason why Christians should be actively persecuted and was thus very lax in carrying out the orders of the first edict. He did indeed have Christian churches demolished, but he did not have anyone executed for professing a different faith.¹⁹⁵

After the abdication of Diocletian and Maximian in 305, acts of persecution gradually faded away. As we shall see, Galerius put a stop to this persecution for good at the end of April 311, only for Maximinus Daia to resume it six months later in the East (where it lasted from late 311 to the beginning of 313, as discussed in Chapter 7); hence, Diocletian’s Great Persecution is usually framed by the years 303 and 313.¹⁹⁶ The most significant consequence that his persecution had was the later schism among Christians about how to deal with the lapsi, i.e. those Christians who had submitted to pressure and made sacrifices, and with the traditores, i.e. bishops who gave up sacred scriptures and objects during the persecution. As Constantine gradually took control of the entire empire in 306–324, responsibility for religious matters within the empire would pass to him and he would intervene in these problems.¹⁹⁷

The following chapter describes, among other things, Diocletian’s abdication (Diocletian’s death will be dealt with in Appendix E); at this point, it would therefore be fitting to briefly review how he reigned and governed. Diocletian was a quite extraordinary figure in the history of the Roman Empire. In many respects, he was extremely talented (but it must also be said that in other ways he was mediocre and had his quite distinct weaknesses): he was able to recognise the needs of the empire and to find adequate solutions to serious and complex problems, and he was good at singling out collaborators suited to these tasks. His genius fully came to the fore in his political, under, military, and fiscal reform of the empire. In the East, Diocletian achieved considerable diplomatic success, although the credit here probably belongs more to his people—the same can be said of his codification of Roman law. As a military leader he was unexceptional, and his monetary reform was a valiant but not entirely successful attempt at rehabilitating the imperial currency. His Edict on Maximum Prices and his persecution of Christians were, in a word, calamitous—the former because it did not take into account the laws of the free market and the latter because it failed to consider people’s compulsion to believe in gods of their own choosing. It is probably no coincidence that Diocletian’s brilliant and successful ideas came to him in roughly the first 10 years of his reign, while the bad and unsuccessful ones tended to be in the last 5 years or so. Nevertheless, his abdication in 305 was one of his greatest achievements. And when he departed for his “retirement” palace in his native land, he left behind an empire in much better shape than he had found it 20 years earlier.

On the whole, Diocletian’s 20 years of rule can also be summarised as having stabilised and elevated the empire economically and militarily to the point where it could afford to engage in internal wars over the next 20 years without collapsing or being looted by the enemy without.