Diocletian

Diocletian may have become involved in battles against the Quadi and Marcomanni immediately after the Battle of the Margus. He eventually made his way to northern Italy and made an imperial government, but it is not known whether he visited Rome at this time.[41] There is a contemporary issue of coins suggestive of an imperial adventus (arrival) for the city,[42][43] but some modern historians state that Diocletian avoided the city, to demonstrate that the city and its Senate were no longer politically relevant to the affairs of the empire.[44] Diocletian dated his reign from his elevation by the army, not his ratification by the Senate,[45] following the practice established by Carus, who had declared the Senate's ratification a useless formality.[46] However, Diocletian offered proof of his deference towards the Senate by retaining Aristobulus as ordinary consul and colleague for 285 (one of the few instances during the Late Empire in which an emperor admitted a privatus as his colleague)[47] and by creating senior senators Vettius Aquilinus and Junius Maximus ordinary consuls for the following year – for Maximus, it was his second consulship.[48] 

Some time after his return, and before 293, Diocletian transferred command of the war against Carausius from Maximian to Flavius Constantius, who concluded it successfully in 296. Constantius was a former governor of Dalmatia and a man of military experience stretching back to Aurelian's campaigns against Zenobia (272–73). He was Maximian's praetorian prefect in Gaul, and the husband to Maximian's daughter, Theodora. On 1 March 293 at Milan, Maximian gave Constantius the office of caesar.[123] The same day, in either Philippopolis (Plovdiv, Bulgaria) or Sirmium, Diocletian did the same for Galerius, husband to Diocletian's daughter Valeria, and perhaps Diocletian's praetorian prefect.[Note 7] Constantius was assigned Gaul and Britain. Galerius was initially assigned Syria, Palestine, Egypt, and responsibility for the eastern borderlands.[127]

This arrangement is called the Tetrarchy, from a Greek term meaning "rulership by four".[128] The Tetrarchs were more or less sovereign in their own lands, and they travelled with their own imperial courts, administrators, secretaries, and armies.[129] They were joined by blood and marriage; Diocletian and Maximian now styled themselves as brothers, and formally adopted Galerius and Constantius as sons. These relationships implied a line of succession. Galerius and Constantius would become Augusti after the departure of Diocletian and Maximian. Maximian's son Maxentius and Constantius's son Constantine would then become Caesars. In preparation for their future roles, Constantine and Maxentius were taken to Diocletian's court in Nicomedia.[130]

Conflict in the Balkans and Egypt[edit]

A Trajanic temple on the island of Philae, the newly established border between the Nobatae and Blemmyes and Roman Egypt[131]

Diocletian spent the spring of 293 travelling with Galerius from Sirmium (Sremska Mitrovica, Serbia) to Byzantium (Istanbul, Turkey). Diocletian then returned to Sirmium, where he remained for the following winter and spring. He campaigned successfully against the Sarmatians in 294, probably in the autumn.[132] The Sarmatians' defeat kept them from the Danube provinces for a long time. Meanwhile, Diocletian built forts north of the Danube,[133] part of a new defensive line called the Ripa Samartica, at Aquincum (Budapest, Hungary), Bononia (Vidin, Bulgaria), Ulcisia Vetera, Castra Florentium, Intercisa (Dunaújváros, Hungary), and Onagrinum (Begeč, Serbia).[134] In 295 and 296 Diocletian campaigned in the region again, and won a victory over the Carpi in the summer of 296.[135] Later during both 299 and 302, as Diocletian was residing in the East, it was Galerius's turn to campaign victoriously on the Danube. By the end of his reign, Diocletian had secured the entire length of the Danube, provided it with forts, bridgeheads, highways, and walled towns, and sent fifteen or more legions to patrol the region; an inscription at Sexaginta Prista on the Lower Danube extolled restored tranquility to the region.[136] The defense came at a heavy cost but was a significant achievement in an area difficult to defend.[137]

Roman fresco on the southern wall of Luxor Temple's imperial cult chamber. It depicts senior military officers gathered around Diocletian's throne, circa 280.[138][139]

Galerius, meanwhile, was engaged during 291–293 in disputes in Upper Egypt, where he suppressed a regional uprising.[136] He returned to Syria in 295 to fight the revanchist Persian empire.[140] Diocletian's attempts to bring the Egyptian tax system in line with Imperial standards stirred discontent, and a revolt swept the region after Galerius's departure.[141] The usurper Domitius Domitianus declared himself Augustus in July or August 297. Much of Egypt, including Alexandria, recognized his rule.[140] Diocletian moved into Egypt to suppress him, first putting down rebels in the Thebaid in the autumn of 297,[132] then moving on to besiege Alexandria. Domitianus died in December 297,[142] by which time Diocletian had secured control of the Egyptian countryside. Alexandria, whose defense was organized under Domitianus's former corrector Aurelius Achilleus, held out probably until March 298.[140][142] Later in 298, the triumphal column now known as Pompey's Pillar was erected in Alexandria to honor Diocletian.[143]

Bureaucratic affairs were completed during Diocletian's stay:[144] a census took place, and Alexandria, in punishment for its rebellion, lost the ability to mint independently.[145] Diocletian's reforms in the region, combined with those of Septimius Severus, brought Egyptian administrative practices much closer to Roman standards.[146] Diocletian travelled south along the Nile the following summer, where he visited Oxyrhynchus and Elephantine.[145] In Nubia, he made peace with the Nobatae and Blemmyes tribes. Under the terms of the peace treaty Rome's borders moved north to Philae and the two tribes received an annual gold stipend. Diocletian left Africa quickly after the treaty, moving from Upper Egypt in September 298 to Syria in February 299. He met with Galerius in Mesopotamia.[131]

War with Persia[edit]

See also: Roman–Iranian relations and Roman–Persian Wars

Invasion, counterinvasion[edit]

Medallion of Diocletian, AD 294

In 294, Narseh, a son of Shapur who had been passed over for the Sassanid succession, came to power in Persia.[147] In early 294, Narseh sent Diocletian the customary package of gifts between the empires, and Diocletian responded with an exchange of ambassadors. Within Persia, Narseh was destroying every trace of his immediate predecessors from public monuments. He sought to identify himself with the warlike kings Ardashir I (r. 226–241) and Shapur I (r. 241–272), who had defeated and imprisoned Emperor Valerian (r. 253–260) following his failed invasion of the Sasanian Empire.[148]

Narseh declared war on Rome in 295 or 296. He appears to have first invaded western Armenia, where he seized the lands delivered to Tiridates in the peace of 287.[149][150] He moved south into Roman Mesopotamia in 297, where he inflicted a severe defeat on Galerius in the region between Carrhae (Harran, Turkey) and Callinicum (Raqqa, Syria), suggested by the historian Fergus Millar to have been somewhere on the Balikh River.[151] Diocletian may or may not have been present at the battle,[152] but he quickly divested himself of all responsibility. In a public ceremony at Antioch, the official version of events was clear: Galerius was responsible for the defeat; Diocletian was not. Diocletian publicly humiliated Galerius, forcing him to walk for a mile at the head of the Imperial caravan, still clad in the purple robes of the Emperor.[153][154][Note 8]

Detail of Galerius attacking Narseh on the Arch of Galerius at Thessaloniki, Greece, the city where Galerius carried out most of his administrative actions[155][156]

Galerius was reinforced, probably in the spring of 298, by a new contingent collected from the empire's Danubian holdings.[157] Narseh did not advance from Armenia and Mesopotamia, leaving Galerius to lead the offensive in 298 with an attack on northern Mesopotamia via Armenia.[158][Note 9] It is unclear if Diocletian was present to assist the campaign; he might have returned to Egypt or Syria.[Note 10] Narseh retreated to Armenia to fight Galerius's force, putting himself at a disadvantage; the rugged Armenian terrain was favorable to Roman infantry, but not to Sassanid cavalry. In two battles, Galerius won major victories over Narseh. During the second encounter, Roman forces seized Narseh's camp, his treasury, his harem, and his wife.[162] Galerius continued down the Tigris, and took the Persian capital Ctesiphon before returning to Roman territory along the Euphrates.[163]

Taxation[edit]

Main article: Capitatio-Iugatio

In the early empire (30 BC – AD 235) the Roman government paid for what it needed in gold and silver. The coinage was stable. Requisition, forced purchase, was used to supply armies on the march. During the third-century crisis (235–285), the government resorted to requisition rather than payment in debased coinage, since it could never be sure of the value of money. Requisition was nothing more or less than seizure. Diocletian made requisition into tax. He introduced an extensive new tax system based on heads (capita) and land (iugera) – with one iugerum equal to approximately 0.65 acres – and tied to a new, regular census of the empire's population and wealth. Census officials traveled throughout the empire, assessed the value of labor and land for each landowner, and joined the landowners' totals together to make citywide totals of capita and iuga.[276] The iugum was not a consistent measure of land, but varied according to the type of land and crop, and the amount of labor necessary for sustenance. The caput was not consistent either: women, for instance, were often valued at half a caput, and sometimes at other values.[277] Cities provided animals, money, and manpower in proportion to its capita, and grain in proportion to its iuga.[276][Note 16]

Most taxes were due each year on 1 September, and levied from individual landowners by decuriones (decurions). These decurions, analogous to city councilors, were responsible for paying from their own pocket what they failed to collect.[279] Diocletian's reforms also increased the number of financial officials in the provinces: more rationales and magistri privatae are attested under Diocletian's reign than before. These officials represented the interests of the fisc, which collected taxes in gold, and the Imperial properties.[238] Fluctuations in the value of the currency made collection of taxes in kind the norm, although these could be converted into coin. Rates shifted to take inflation into account.[276] In 296, Diocletian issued an edict reforming census procedures. This edict introduced a general five-year census for the whole empire, replacing prior censuses that had operated at different speeds throughout the empire. The new censuses would keep up with changes in the values of capita and iuga.[280]

Italy, which had long been exempt from taxes, was included in the tax system from 290/291 as a diocesis.[281] The city of Rome remained exempt; the "regions" (i.e., provinces) South of Rome (generally called "suburbicarian", as opposed to the Northern, "annonaria" region) seem to have been relatively less taxed, in what probably was a sop offered to the great senatorial families and their landed properties.[282]

Diocletian's edicts emphasized the common liability of all taxpayers. Public records of all taxes were made public.[283] The position of decurion, member of the city council, had been an honor sought by wealthy aristocrats and the middle classes who displayed their wealth by paying for city amenities and public works. Decurions were made liable for any shortfall in the amount of tax collected. Many tried to find ways to escape the obligation.[279] By 300, civilians across the empire complained that there were more tax collectors than there were people to pay taxes.[284]

Currency and inflation[edit]

A fragment of the Edict on Maximum Prices (301), on display in Berlin

Part of the prices edict in Greek in its original area built into a medieval church, Geraki, Greece

Aurelian's attempt to reform the currency had failed; the denarius was dead.[285] Diocletian restored the three-metal coinage and issued better quality pieces.[286] The new system consisted of five coins: the aureus/solidus, a gold coin weighing, like its predecessors, one-sixtieth of a pound; the argenteus, a coin weighing one ninety-sixth of a pound and containing ninety-five percent pure silver; the follis, sometimes referred to as the laureatus A, which is a copper coin with added silver struck at the rate of thirty-two to the pound; the radiatus, a small copper coin struck at the rate of 108 to the pound, with no added silver; and a coin known today as the laureatus B, a smaller copper coin struck at the rate of 192 to the pound.[287][Note 17] Since the nominal values of these new issues were lower than their intrinsic worth as metals, the state was minting these coins at a loss. This practice could be sustained only by requisitioning precious metals from private citizens in exchange for state-minted coin (of a far lower value than the price of the precious metals requisitioned).[288]

By 301, the system was in trouble, strained by a new bout of inflation. Diocletian, therefore, issued his Edict on Coinage, an act re-tariffing all debts so that the nummus, the most common coin in circulation, would be worth half as much.[289] In the edict, preserved in an inscription from the city of Aphrodisias in Caria (near Geyre, Turkey), it was declared that all debts contracted before 1 September 301 must be repaid at the old standards, while all debts contracted after that date would be repaid at the new standards.[290] It appears that the edict was made in an attempt to preserve the current price of gold and to keep the Empire's coinage on silver, Rome's traditional metal currency.[291] This edict risked giving further momentum to inflationary trends, as had happened after Aurelian's currency reforms. The government's response was to issue a price freeze.[288]

The Edict on Maximum Prices (Edictum De Pretiis Rerum Venalium) was issued two to three months after the coinage edict,[285] somewhere between 20 November and 10 December 301.[290] The best-preserved Latin inscription surviving from the Greek East,[290] the edict survives in many versions, on materials as varied as wood, papyrus, and stone.[285][292] In the edict, Diocletian declared that the current pricing crisis resulted from the unchecked greed of merchants, and had resulted in turmoil for the mass of common citizens. The language of the edict calls on the people's memory of their benevolent leaders, and exhorts them to enforce the provisions of the edict, thereby restoring perfection to the world. The edict goes on to list in detail over one thousand goods and accompanying retail prices not to be exceeded. Penalties are laid out for various pricing transgressions.[293]

In the most basic terms, the edict was ignorant of the law of supply and demand: it ignored the fact that prices might vary from region to region according to product availability, and it ignored the impact of transportation costs in the retail price of goods. In the judgment of the historian David Potter, the edict was "an act of economic lunacy".[294] The fact that the edict began with a long rhetorical preamble betrays at the same time a moralizing stance as well as a weak grasp of economics – perhaps simply the wishful thinking that criminalizing a practice was enough to stop it. There is no consensus about how effectively the edict was enforced.[295]

Supposedly, inflation, speculation, and monetary instability continued, and a black market arose to trade in goods forced out of official markets.[296] The edict's penalties were applied unevenly across the empire (some scholars believe they were applied only in Diocletian's domains),[288] widely resisted, and eventually dropped, perhaps within a year of the edict's issue.[297] Lactantius has written of the perverse accompaniments to the edict; of goods withdrawn from the market, of brawls over minute variations in price, of the deaths that came when its provisions were enforced. His account may be true, but it seems to modern historians exaggerated and hyperbolic,[298] and the impact of the law is recorded in no other ancient source.[299]