The period which these orations covers may most easily be subdivided into reigns, or a series of reigns, as follows (ignoring usurpers):

A. Anarchy and recovery (Gallienus to Carus and his sons: 253-285)
B. Diocletian and the Tetrarchy (285-306)
C. Constantine and his rivals (306-324)
D. Sole rule of Constantine (324-337) and the house of Constantine (337-363)
E. Jovian; Valentinian and Valens, Gratian (363-383) (I arbitrarily end the period with the death of Gratian; although Valentinian II lived until 392, he never ruled independently.)
F. Theodosius' (virtual) sole rule (383-395)

The Panegyrici latini are public orations epideictic in form but political in nature; their authors' interests are in large part the emperors' praiseworthy exertions in war and in peace. Consequently the subsequent narrative is primarily military and political, to give an outline of those categories of events to serve as a frame of reference for the reader. This will be a rehearsal of reigns, after the manner of the fourth-century breviaries. It will not be a thorough history of the period, not only because its brevity seeks to exclude even many details of military and political history, but because the basic framework has no place for a reasonable discussion of economic, social, literary, artistic, philosophical or religious developments.

A. One may well begin with the panegyrist of Constantius and regard the empire as it existed under Gallienus. That orator says:

At that time both the Parthian had too lofty pretensions and the Palmyrene claimed equality; all of Egypt and the Syrias had seceded, Raetia was lost and Noricum and the Pannonias devastated. Italy herself, mistress of nations, lamented the destruction of very many of its cities. There was not so much distress over individual losses when the empire was deprived of almost everything (Pan. 8.10.2-3).

Rulers who must maintain their position have less time to attend to external affairs than those whose rule is undisputed, yet pressures on the empire from without grew during the third century. Marcus Aurelius died (in 180) fighting a war against the Marcomanni; successive waves of Germanic peoples continued to trouble the Romans over the course of the next several centuries until, and indeed after, the fragmentation of the western part of the empire. Nomadic tribes in North Africa made periodic irruptions into the more settled areas of the southern Mediterranean shore. Egypt, from the time Augustus made it a province, was the scene of more than one local rebellion. The large kingdom of the Parthians had caused problems for the eastern provinces from the very beginning of the imperial period. Now, however, there arose in Persia the new and vigorous dynasty of the Sassanians. The first ruler of the dynasty, Ardashir, consolidated the power which his successor, Sapor (Shapur) I, had inherited in 241.

Gallienus' reign indeed witnessed the fragmentation of the Roman empire. His father Valerian was captured by the Persians in 260 and ended his life in captivity. In the same year in the west, the usurper Postumus took over what is known as the Imperium Galliarum, the group of northwestern provinces whose rulers remained unrecognized by any of the legitimate Roman emperors, but which stayed outside the empire until Aurelian reclaimed it in 274. (For a history of the Imperium Galliarum see J.F. Drinkwater, The Gallic Empire, A.D. 260-274 (Historia Einzelschriften Band 52) (Stuttgart 1987). Goths invading Asia Minor and the Balkans claimed the attention of Gallienus and his immediate successors. Odenathus, the ruler of Palmyra, successfully undertook on Rome's behalf the struggles against both Persia and a pretender in Egypt; after his death in 267 his widow Zenobia continued to create what was really an independent state until Aurelian defeated her in 273.

Gallienus was assassinated in 268. The more important and successful of his recognized successors are Claudius II (268-270), given the cognomen Gothicus, who died of natural causes while fighting the Goths, Aurelian (270-275), who succeeded in reuniting the fragments of the Roman empire, Probus (276-282) and Carus (282-283), who reinforced the work of consolidation and successfully prosecuted the long-standing war against Persia. Carus' sons Numerian and Carinus succeeded him; when Numerian died in 284, due to the treachery, it was believed, of his father-in-law Aper, the army elected an officer called Diocles (afterwards Diocletian) ruler in the east. In 285 Diocletian became sole ruler at the death of Carinus, who probably fell at the hands of one of his own officers. The empire of which Diocletian found himself the head had suffered from economic and social dis¬ruption accompanied not only by actual physical destruction of cities, towns, and country dwellings, but by the more intangible damage done to Roman morale. It is to his credit that he performed his task of restoration as well as he did.

B. Diocletian spent most of his reign in the eastern half of the empire. To care for the western portion he appointed his associate Maximian, a man who, like himself, had had a military career. He may originally have appointed Maximian as merely a general, but more likely as his Caesar; by the end of 286 Maximian was an Augustus, although second in rank to Diocletian. Diocletian added the titles Iovius (for himself) and Herculius (for Maximian) to indicate the relative authority of the two Augusti. Maximian's immediate task was to pacify Gaul, overrun by local peasants who were called Bagaudae. Securing the borders (especially the Rhine border) against Germanic invaders was another pressing task, and, finally, Maximian was faced with the pretender Carausius, who had turned a legitimate naval command in the English Channel into a bid for co-rulership, and who held the provinces of Britain.

For his part, Diocletian had negotiated a favorable peace with Persia early in his reign, but faced renewed war on that front in the 290's, at the same time that he was campaigning to pacify the Danube frontier. In 293 two Caesars were created, to form an imperial college of four. In the west, Constantius became Maximian's heir apparent, and married that Augustus' daughter or step-daughter Theodora. Galerius became the eastern Caesar and married Diocletian's daughter Valeria. Much ink has been spilt on the origin of this tetrarchy, especially in view of the western Caesar's being senior to the eastern one. Although one cannot ascertain whether Diocletian intended from the beginning to create a college of rulers, the fact is that by the end of his reign such a system was in place.

The accomplishments of the Tetrarchy were many. The eastern part of the empire saw the pacification of two rebellions in Egypt (the occasions and dates given for these rebellions vary considerably in the scholarship. There is no consensus, but the majority opinion now inclines to a time around 294 for the earlier rebellion in the vicinity of Coptos, and of 297/8 for the later one, centered in Alexandria.), Galerius' splendid victory over the Persians in 297/8, and a decade more of operations along the Danube. Constantius, or rather his praetorian prefect Asclepiodotus, recovered Britain in 296, and the western Caesar could also claim several successes in campaigns against Germanic marauders during the final years of the third century or early in the fourth. At the same time the rulers sought, with mixed success, to reorganize the provincial administration, to ensure internal security, to rebuild what had fallen into disrepair, and to restore financial prosperity. The early fourth century saw both Diocletian's unsuccessful effort to control wages and prices (in 301 Diocletian issued his Edict on Maximum Prices, which he hoped, along with reform of the currency, would bring financial stability to the empire) and the last large-scale persecution of Christians, undertaken while Diocletian still ruled and continued under his successors Galerius and Maximinus Daia.

In 305, after twenty years of rule, Diocletian announced that he and his colleague Maximian would retire. Debate continues as to whether the retirement was long planned, or whether Galerius prevailed upon his ailing superior to lay aside the cares of state and devote himself to his garden (Lactantius' version: Mort. 18). However that may be, Diocletian did abdicate and required Maximian to do the same. The two Caesars were promoted to Augusti, and each then adopted a Caesar to serve under him: Severus in the west, and in the east, Maximinus Daia. The adoption of Caesars, both believed to be Galerius' men, ignored the grown sons of the western rulers. Nevertheless, there was a smooth transition of power, and the tetrarchic system lasted for another year, until the death of Constantius at York in July 306. Without waiting to hear the wishes of the remaining Augustus, the army in Britain proclaimed Constantius' son Constantine their new ruler. While Galerius eventually accepted the proclamation, he promoted Severus to western Augustus and confined Constantine to the rank of Caesar. The Tetrarchy had tottered, but not fallen.

C. After Constantine's successful usurpation, for that was what it was, the empire witnessed a series of internal power struggles. In October 306 in Rome the Praetorian guard announced their choice of Maxentius, Maximian's son, as yet another emperor. Maxentius persuaded his father to return from retirement and together the two won over the army of Severus, who had invaded Italy to put down the pretender. Severus died in captivity. Galerius in person had no better success, but prudently withdrew from Italy before suffering his colleague's fate. Constantine, nominally allied with Maximian since his marriage in 307 to the latter's daughter Fausta and his simultaneous promotion to Augustus by his new father-in-law, remained with his army in Gaul and aided neither side. Subsequently, Maximian and his son had a falling out and after the army supported the younger man Maximian fled to his son-in-law in Gaul.

Galerius, his grip on affairs seriously weakened, persuaded Diocletian to emerge from retirement to hold the consulship for 308 with him and lend his authority to the government. In November 308 they called a council at Carnuntum to constitute the Tetrarchy anew. The result was a victory for Galerius, with an innovation sanctioned by the architect of the system. His old army friend Licinius, who had been sent as an envoy to Maxentius the year before (Anon.Val. 3.7), became Augustus in Severus' stead without having been Caesar first. A disappointed Constantine was told to be content with the title Caesar and Maximian was obliged to retire once more. He went to live with Constantine and Fausta in Gaul. Maximinus Daia, who like Constantine had seen an Augustus promoted over his head, remained an equally discontented Caesar, and Maxentius was ignored. In 310, while Constantine was absent fighting the Franks, Maximian persuaded part of the western army to support him in yet another bid for power and established himself in Arles. Constantine made a lightning journey south and Maximian retired behind the formidable walls of Marseilles. After an unsuccessful siege of the city, Maximian gave himself up to Constantine, only to die, by his own hand according to the official story. In the east, Galerius was suffering from the illness which, despite his cessation of the persecution of Christians, was to kill him (a form of "tyrant's disease," a disgusting death visited upon those thought to be the most deserving. For the syndrome (phthiriasis, evidently), see T. Africa, "Worms and the Death of Kings," Classical Antiquity 1 (1982) 1-17), and Licinius and Maximinus Daia were poised to see who would claim more of Galerius' territory when he died. Maxentius still held Italy and Africa. Although it was officially Licinius' task to remove Maxentius, and Maxentius himself had fortified northern Italy against aggression from the east, early in 312 Constantine left Gaul with a relatively small force and invaded Italy. He encountered stiff resistance at several places in the north of the peninsula, but finally advanced to Rome and in October of that year met his rival outside of the city near the Milvian bridge. The eve of the victory traditionally marks Constantine's conversion to Christianity (Lactantius Mort. 44.5-6, Eusebius VC 1.28-30). Maxentius, fleeing in defeat, was drowned in the Tiber, and Constantine entered the city as liberator. He had meanwhile added Italy and Africa to his territory, which already included the provinces of Britain, Gaul, and Spain. On his return to the north in 313 Constantine met with Licinius in Milan. The two agreed to form an alliance, and Licinius married Constantine's half-sister Constantia as part of the agreement. Subsequently, in the same year, Licinius defeated Maximinus Daia and took over his territories in the eastern part of the empire; the persecution of Christians, which Maximinus Daia had prosecuted vigorously after Galerius' death, now ceased.

There were now only two rulers, Constantine in the west and Licinius in the east. Each followed a policy of religious toleration and for several years managed to remain at peace. In 316 war broke out between the two on one pretext or another (one might consult with profit T. D. Barnes, Constantine and Eusebius 66-67) and following two victories in the field Constantine nevertheless found himself in such a precarious position that he was willing to negotiate a settlement whereby Licinius remained in power but lost almost all of his European territory. In 317 three Caesars were created: Constantine's son Crispus by an early marriage and his new son Constantinus, and Licinius' young son Licinius. An uneasy peace lasted for half a dozen years. As early as 321 Licinius' Christian policy found disfavor, but open warfare did not occur until later. In 323, while defending the empire against the Sarmatians, Constantine's army seems to have found itself in Licinius' territory, and the eastern emperor raised objections. Strictly speaking, Tetrarchic (or Dyarchic) custom ignored geographical boundaries, especially in military emergencies: Licinius' reaction demonstrates the political reality of the arrangement. In 324 Constantine and Licinius went to war. The western emperor was victorious by land and, thanks to his son Crispus, by sea. That same year Licinius was deposed (and later executed), and Constantine became sole ruler of the Roman empire.

D. There is no extant Latin panegyric to celebrate Constantine's remaining thirteen years of life. One may most conveniently consult the Greek, and Christian, orations of Eusebius of Caesarea, composed late in Constantine's reign, in H. A. Drake's In Praise of Constantine. A Historical Study and New Translation of Eusebius' Tricennial Orations (Berkeley 1976). Of his many deeds which most profoundly affected posterity one may mention in particular the development of a mobile army to complement the forces now stationed permanently on the borders, the continuation of Diocletian's financial system of tax assessment and collection, and the issue of a sound gold currency, his embracing of Christianity with his involvement as emperor in church controversies, and the expansion and renaming of the city of Byzantium to become Constantinople, the second Rome. Constantine had had his son Crispus executed in 326 for reasons which posterity can guess at but never know for sure (for some reconstructions, see P. Guthrie, "The Execution of Crispus," Phoenix 20 (1966) 325-331; T.D. Barnes, Constantine and Eusebius 220-221). When he died in 337 he left the empire and a nascent war with Persia to three sons by Fausta and to a nephew; a massacre soon after his death left his sons in power but removed all of his other close male relatives except two young children, Gallus and Julian, sons of Julius Constantius.

Constantine's remaining three sons divided up the empire, but by 350 only Constantius II survived. His long reign was characterized by conflicts with Persia, civil wars, and religious disputes. Against Magnentius in particular, who had removed Constans from power in the west, Constantius fought a protracted civil war which cost the empire thousands of lives; finally in 353 he reunited the empire under his own name. To assist him in the task of governing so unwieldy a realm Constantius, who was childless, appointed as Caesar his cousin Gallus, the older surviving son of Julius Constantius, but before the end of 354 he had recalled Gallus and had him executed. Ammianus Marcellinus book 14 may be consulted for a lurid account of the end of Gallus' reign.

Constantius remained in the north campaigning against the Alamanni; his reign also saw the short-lived usurpation of Silvanus. In 355 Constantius sent his only surviving male relative, his cousin Julian, to Gaul as Caesar. With Julian in residence, the northwestern provinces began to recover from the foreign incursions and economic depression which had characterized the years since the assassination of Constans. But Sapor II of Persia renewed his aggression against Roman territory and Constantius tried none too successfully to fend him off. At the end of 359 he sent to Gaul to ask Julian to send him military reinforcements, and many of the soldiers apparently refused to contemplate leaving their homes to go to the far east. In 360 at Paris the soldiers proclaimed Julian Augustus. After negotiations lasting over a year, Julian marched east against his cousin. Constantius, however, died of a disease in November 361, and the empire was spared another civil war.

Julian's term as sole Augustus was not to last long. He spent the year 362 in the east, preparing for a war against Persia while he actively undertook to restore Romans to the worship of the pagan gods. While promoting religious freedom in some respects (he recalled Christians exiled under his Arian predecessor), Julian refused to allow Christians to teach classical literature, the foundation of the educational system, and as time went on he discriminated against Christians (including, traditionally, the later emperor Valentinian I) in his administration. In 363 Julian embarked upon an invasion of Persia; he died in the same year, having received a mortal wound in battle. Jovian, the army's choice of successor, negotiated an unfavorable, if necessary, treaty of peace with Persia and retreated. Within the year he was dead, the victim of accidental asphyxiation.

E. After some discussion, the army chose a new emperor in February 364: Valentinian, a Pannonian officer, who subsequently, upon the insistence of the soldiers, chose a colleague, his younger brother Valens, to whom he left the administration of the eastern part of the empire. By the end of 365, Valentinian was in Gaul, where the absence of a ruler had encouraged the Romans' neighbors to embark upon invasions. Leaving his brother to deal with the pretender Procopius, Valentinian concentrated upon the pacification of Gaul and Britain, where for the next decade he and his generals served the empire with great success. Valentinian's program included the building of forts along the limes to secure the gains of his military campaigns. His contemporary Ammianus devotes much less space to Valentinian's or his brother's accomplishments than to the rehearsal of court intrigue and worse: Valentinian seems to have trusted excessively in unworthy subordinates, and the reign of Valens, until its spectacular end, was most noteworthy in the historian's pages for the hunting down of real or imaginary pretenders. In 367 there were three rulers of Valentinian's house, for he had in that year appointed his son Gratian co-emperor. Consequently, when Valentinian died suddenly in 375 there was no need of another election. Several of the army leaders, however, named young Valentinian II (four years old at the time) Augustus as insurance against possible usurpation, and Gratian accepted their choice.

In 375 Gratian's and Valens' greatest military problems were in the north. Gratian had overseen several campaigns against the Alamanni, and there was Gothic pressure on the Danube frontier. After a badly mismanaged attempt, begun in 376, to settle the Goths in Roman territory, Valens found himself facing an insurrection. At Adrianople in 378, he and his forces faced the invaders alone. In the battle which ensued, Valens and the greater part of the Roman army were killed. In the crisis Gratian appointed the retired general Theodosius to the command in the east and in 379 made him Augustus. Theodosius, whose main residence was at Constantinople, eventually came to a negotiated agreement with the Goths, who settled in the empire. Gratian remained in the west.

F. In 383 the commander of the army in Britain, Magnus Maximus, usurped the throne, crossed to Gaul, and disposed of Gratian. Several years of ambiguous relations accompanied by sporadic negotiations with the courts of both Valentinian II and Theodosius ensued. Theodosius' attitude, to judge from his failure to take military action against Maximus, seems to have been acquiescence; religious difficulties compounded the political question. Valentinian and his mother Justina were Arians, and Theodosius' Christianity was orthodox; while Maximus' orthodoxy need not have been a point in his favor, the religious orientation at the court of Valentinian II would have been repugnant to the very pious eastern ruler. At any rate, Theodosius remained in the east while Maximus ruled, apparently rather well for the most part, in Spain, Gaul, and Britain. There was, however, one stain on his record.

For some years past the existence of an ascetic Christian sect, connected with Gnostic beliefs, had caused disturbances in the Spanish churches. The leader of the sect, Priscillian, had been ordained as bishop of Avila, but had had to leave Spain for Gaul to seek help to maintain his position. Although Priscillian obtained no religious authority for resuming his see, he was able to get from Gratian's court an imperial rescript in his favor. Maximus, however, soon became the ruler in Gaul and he was persuaded to assume a severe view toward Priscillian and his followers, who were tried on charges of magic. Priscillian and four others were executed, despite the protests of Martin of Tours, and still others were exiled. The charge was ostensibly a criminal offense, but no one failed to see a precedent in the trial and punishment of religious differences in a lay court.