The decline of the Roman empire
DIOCLETIAN and CONSTANTINE
Diocletian and the Tetrarchy
Unlike the previous soldier-emperors from the Danubian area Diocletian (1) had no outstanding gifts as a general, although he was a competent soldier. But he exhibited capacity, or at any rate energy, such as was rarely found among later Roman emperors. It soon became clear that he had pondered over the problems of the Empire and had plans ready to meet them. A new start must be made; no longer could one emperor sit at Rome and control the whole web of interests. He must be in the field where frontiers were threatened. But his personal presence was demanded on many frontiers, since if he sent generals they might be tempted to continue the dreary process of attempted usurpation.
Diocletian therefore decided to move around with his staff and court (comitatus) as needed (in fact throughout his reign he visited Rome only once) and at the same time to supplement his own efforts by appointing helpers of outstanding authority. In 285 therefore he named a Danubian compatriot, M. Aurelius Valerius Maximianus (2), as Caesar, and while he himself took the title Jovius he granted the name of Herculius to Maximian. The two men would act together under the shield of their patron gods, the greater god being assigned to the greater ruler, while the humble origin of the two emperors might be forgotten in the gleam of this new celestial light. In the following year Maximian was given the rank of Augustus as a reward for his efficient crushing of a revolt in Gaul of wandering bands of discontented peasants and others named the Bagaudae. Intermittently for the next four or five years Maximian had to contend with attacks across the upper Rhine by Alamanni and Burgundi, while further north the Franks had to be checked. In 288 a Frankish chief accepted peace in return for the title of King of the Franks. Maximian was less successful in his attempt to clear the English Channel of Saxon and Frankish pirates, since a Messapian named M. Aurelius Mausaeus Carausius (3), whom he had appointed as commander of a fleet based at Gesoriacum (modern Boulogne), crushed the pirates but decided to use his naval power to proclaim himself "Augustus" and to occupy Britain, where he set up a local empire on the model of Postumus' imperium Galliarum (287).
He was thus able to defy Maximian, who reached a working agreement with him in 290. During these years Diocletian was based at Nicomedia in Bithynia, where he went to the Danube to defeat the Sarmatae (289 and 292), to Syria against Saracen invaders (299), and to Egypt to crush a revolt of the native Blemmyes (291). He also secured an Arsacid on the throne of Armenia without provoking Persia to war.
Although for many years Maximian had played his part well, in much the same relationship to Diocletian as Agrippa to Augustus, in 293 Diocletian carried the delegation of functions a stage further. One emperor could not be omnipresent, but four could cover more ground than two. He therefore nominated two young officers, C. Flavius Valerius Constantius (4) (usually known as Constantius Chlorus), who was also of Illyrian-Danubian origin, and C. Galerius Valerius Maximianus (5) to a share of the imperial power.
While Diocletian and Maximian were nominally joint emperors (like M. Aurelius and L. Verus) and shared the title of Augustus, Galerius and Constantius were styled Caesars and became heirs-expectant to the two senior rulers. The division of the competence between Diocletian and his colleagues was made on a territorial basis. While the senior partner reserved for himself the eastern provinces he assigned Italy, Africa, Spain and the northern frontier provinces to Maximian, whose Caesar, Constantius, received Gaul and Britain; while himself assuming responsibility for the East and Egypt, Diocletian most of the Balkans to his Caesar, Galerius. The primary object of establishing this quattuorvirate was undoubtedly military, but it was also intended to provide for an orderly succession. At first sight the plan might appear as a revival of the triumvirates which had hastened rather than retarded the fall of the Republic, yet under Diocletian's supervision it worked well. By virtue of his personal authority the chief partner remained in effect the sole emperor, while he secured the loyal assistance of three of the ablest military commanders. Constantius, who had been praetorian prefect, had already married Maximian's step-daughter (and put away Helena, the mother of Constantine); he was a man of statesmanlike qualities. Galerius divorced his wife in order to marry Diocletian's daughter, Valeria; he was a much rougher diamond, even if the unflattering portrait drawn by Christian writers of this persecutor of their fellow Christians is exaggerated.
Although Diocletian's reign was not free from attempted usurpations, these did not lead to any general recurrence of civil war. In 296 an adventurer named L. Domitius Domitianus with a helper named Achilleus assumed the imperial title in Alexandria, but was promptly crushed by Diocletian in person. More serious was Carausius's claim to be a third Augustus; he must be brought to heel at last. On the whole Britain had escaped many of the troubles of the third century, except inflations, and Carausius had organized the defense of the east and south coasts against the Saxons by building some of the so-called Saxon Shore forts (such as Richborough, Lympne and Portchester). However, he was murdered and supplanted by a subordinate named Allectus in 293, against whom Constantius mounted an invasion in 296. While Constantius made a demonstration in the Channel, his praetorian prefect, Asclepiodotus, eluded the enemy fleet in a mist and landed near Southampton Water. He then defeated Allectus's army near Silchester, while Constantius's forces sailed up the Thames River just in time to save London from some of Allectus's defeated but marauding troops. Constantius's arrival (redditor lucis aeternae) is depicted on a famous gold medallion found near Arras (6). Thus with the collapse of the imperium Britanniarum the unity of the Empire was restored.
In the absence of continuous civil wars Diocletian's colleagues were able to give a good account of themselves in frontier defense. Maximian, followed by Constantius (297-298), crushed invasions by the Alamanni in Gaul, Galerius kept order on the Danube, and Maximian in 298 subdued the Quinquegetani, a Moorish tribe in Africa (later that year Maximian appears to have visited Rome for the first time in his reign). In 296 Diocletian was called upon to defend Mesopotamia, which had been ceded by the Persian king Bahram in 284. A new and vigorous king named Narses declared war. Diocletian entrusted the conduct of this Persian war to Galerius, who made good an initial defeat on open ground near Carrhae by transferring operations to Armenia, destroying Narses's army in a second battle and capturing Ctesiphon. Diocletian did not follow up on his lieutenant's success, but he restored Roman suzerainty and was apparently content to let the Roman frontier lie on the line from Nisbis to Singara, with control over the whole of the upper Tigris basin. The alliance with Armenia was subsequently strengthened by the conversion of its ruler Tiridates III (261-317) to Christianity, which definitely estranged him from the Sassanids, even if it did not draw him nearer to the Caesars. With these operations the frontiers were made safe for the time being against major invasions, and an anxious period of forty years, in which crisis followed crisis, drew to a close. Furthermore, the Tetrarchy had stood the strains to which it was subjected during this middle period of Diocletian's reign.
The system of Diocletian appeared to have justified itself by its results. But its success was due largely to the personal ascendancy of the emperor, for it was this and not the system itself that checked the ambitions of his colleagues. But he was getting older and feeling the burden of rule, while in the early years of the new century he had to face the divisive aspect of Christianity in the Empire and pressure from Galerius. Thus in late 303 when he went with Maximian to Rome to celebrate his twentieth anniversary as emperor he decided that both men should retire early in 305 after Maximian had celebrated his vicennalia in turn, and he extracted an oath from his colleague to fulfill his promise. On May 1, 305, therefore, Diocletian formally abdicated at Nicomedia and Maximian at Milan, and their Caesars, Galerius and Constantius, succeeded them as Augusti. But the appointment of two new Caesars was less easy. On a dynastic principle the two obvious candidates were Maxentius, son of Maximian, and Constantine, the bastard son of Constantius. But Diocletian did not consider the former suitable and therefore thought it wiser to pass them both by. The new Caesars were Flavius Valerius Severus, an Illyrian friend of Galerius, in the West, and C. Galerius Valerius Maximinus Daia (7), Galerius's nephew, in the East.
By the territorial division which followed, Constantius held Britain, Gaul and Spain, and his Caesar, Severus, had Africa, Italy and Pannonia. Galerius received Asia Minor west of the Taurus Mountains, while Maximinus had the other Asiatic provinces and Egypt. Although theoretically Constantius was the senior Augustus, Galerius seemed to have gotten the best of the bargain, since through Severus he could control much of the West and at the same time put pressure on Constantius since he held his son Constantine at his own court. Under this arrangement the Roman Empire was virtually partitioned into separate and rival sovereignties, as in the days of the second triumvirate, and Diocletian's retirement, an act of self-denial, which in its intentions and results, recalled the abdication of Sulla, threw the constitution back into the melting pot. Diocletian's great palace and his luxurious baths were dedicated in 305-306 A.D.
Diocletian's Palace in Split - Croatia,
built for his retirement after he abdicated in 305 A.D.
The baths of Diocletian, shown in the top half of the photo.
The Rise of Constantine
While Diocletian contentedly cultivated vegetables in his great palace at Salona (modern Split) and Maximian reluctantly endured retirement in Lucania, the pattern of power changed rapidly. Constantius, who already had carried through some reconstruction in Britain, was needed there again, either to punish or anticipate attacks by the Picts (Caledonians) in the north of the province. He seized this chance to ask Galerius to let his son Constantine (8) join him for the campaign. Galerius could hardly refuse this request unless he was prepared for civil war. Constantine however, took no chances. He traveled by forced marches and killed the past-horses behind him, since even if Galerius took no direct action, traveling through Severus's territory might prove hazardous. However, he safely joined his father at Boulogne early in 306 and together they carried through a campaign which reached the north of Scotland. But after this victory Constantius died at York, and the army proclaimed Constantine as Augustus in his father's place. While waiting for Galerius's reply to a request for recognition Constantine strengthened his position by leading his main army from Britain to southern Gaul, where he learned that Galerius had compromised. Severus was to be the new Augustus, but Constantine was recognized as Caesar. He gave in for the moment; civil war was averted and the tetrarchy was saved.
Constantine's success goaded Maximian's son Maxentius (9), to become the figurehead, if not the spearhead, of a revolt in Rome caused by taxation and the suppression of the Praetorian Guard (October 306). This popular movement elevated Maxentius as Pinceps (he avoided claiming any more provocative title); he was accepted by southern Italy and Africa, but northern Italy stood by Severus. Support of the Praetorians and urban cohorts would not carry him far, so he successfully appealed to his father Maximian to come out of retirement to help him. Galerius's reaction was to order Severus to march on Rome. But Maximian resumed his title of Augustus and drove Severus back to Ravenna, where he was captured. Maxentius was proclaimed Augustus in 307.
In order to face the expected counter-attack by Galerius, Maxentius sought the support of Constantine, whom he won over by giving him his sister Fausta in marriage and acknowledging him as Augustus in return for similar recognition. Galerius's invasion was not long delayed and he reached as far as Interamna without opposition. However, he lacked the means for an attack on Rome itself, his troops became disaffected and he was forced to retire, while Maxentius curiously made no effort to hamper his retreat. In the meantime Severus had been put to death in captivity. Maxentius next found himself double-crossed by his own father, who tried to persuade Constantine to come south in order to crush the retreating Galerius and then Maxentius. Constantine refused, although he broke off relations with Maxentius when he heard that Spain had declared for him. So the father was left to tackle his son alone. Late in 307 Maximian went to Rome and after a few months of joint rule he tried to overthrow Maxentius, tearing his purple robe from him. But he misjudged the temper of the soldiers, who rallied to the son and forced Maximian to flee to his son-in-law Constantine, leaving Maxentius in control of Rome (early 308).
Galerius attempted a new settlement by appealing to the aged Diocletian to come out of his retreat and attend a conference at Carnuntum which Maximian also attended in November 308. Diocletian refused to reassume the purple and persuaded his old colleague Maximian to retire again. Galerius nominated an old companion in arms Licinianus Licinius (10)
to succeed Severus as junior Augustus with control of Italy, Africa and Spain (which in fact were held by Maxentius who was now declared a usurper); Maximinus continued as Caesar in the East, while Constantine was demoted in rank to Caesar of Gaul and Britain. The two Caesars refused to be placated by the title of "Sons of the Augusti", and so in 310 Galerius had to agree to their claim to be Augusti. Thus there were now four Augusti (Galerius, Licinius, Constantine and Maximinus), while Maxentius was unrecognized, although he held Italy, Africa and Spain. However, a Domitius Alexander had been proclaimed Augustus in Africa, and Spain went over to Constantine. If Galerius had reason to be satisfied with what was settled at Carnuntum, Constantine was greatly strengthened by the reshuffling.
In 310 one major piece disappeared from the chess-board. Maximian, who had returned to his son-in-law Constantine in Gaul, tried to win over some troops while Constantine was busy campaigning against the Franks. The coup failed and Constantine probably acquiesced in, if he did not order, his death. Thus a link snapped between Constantine and the "Herculius" Augustus, who had first recognized him as Augustus, so Constantine began to look for a new basis for his authority. He propagated the idea that his father, Constantius, was descended from Claudius Gothicus, and adopted the Unconquered Sun (Sol Invictus) in place of Hercules as the patron of the dynasty. Early in 311 two claimants to power were removed. In Africa Alexander was killed by an expedition sent by Maxentius, while Galerius died after an illness which he attributed to the God of the Christians whom he had mercilessly persecuted; a death-bed repentance resulted in an edict granting greater tolerance to Christians, but not in his recovery.
The four survivors played for position. Maximinus Daia overran Asia Minor before Licinius could, and then reached an agreement with him. Constantine, anticipating a struggle against Maxentius, made an agreement with Licinius (who was engaged to his sister Constania). This in turn drove Maximinus into the arms of Maxentius in Italy. Early in 312 war was declared, and Constantine advanced from Gaul.
Constantine's forces were heavily outnumbered by at least two to one, perhaps even four to one, but he struck hard and fast. Maxentius's main forces were posted near Verona (perhaps to guard or force the Brenner Pass against Licinius). Constantine swept over the Alps by the Mont Cenis, and defeated a large force, including clibanarii (heavily armed cavalry) near Turin, which fell to him, while Milan surrendered. Advancing to Verona he won a decisive victory and was master of northern Italy.
.. to be continued.
Compiled by Marko Marelich
Retired Mechanical Engineer
San Francisco, California USA
July 4th, 2006