was born near Salona in Dalmatia, in the year A. D. 245, of most obscure parentage; his father, according to the accounts commonly received, which are, however, evidently hostile, having been a freedman and provincial scribe, while the future emperor himself was indebted for liberty to a senator Anulinus. Were this last statement true he must have been born while his parent was a slave; but this is impossible, for, as Niebuhr has pointed out, the Roman law, even as it stood at that period, would have prevented the son from being enlisted in the legion. From his mother, Doclea, or Dioclea, who received her designation from the village where she dwelt, he inherited the appellation of Docles or Diocles, which, after his assumption of the purple, was Latinized and expanded into the more majestic and sonorous Diocletianus, and attached as a cognomen to the high patrician name of Valerius. Having entered the army he served with high reputation, passed through various subordinate grades, was appointed to most important commands under Probus and Aurelian, in process of time was elevated to the rank of consul suffectus, followed Carus to the Persian war, and, after the death of that emperor on the banks of the Tigris [CARUS], remained attached to the court during the retreat in the honourable capacity of chief captain of the palace guards (domestici). When the fate of Numerianus became known, the troops who had met in solemn assembly at Chalcedon, for the purpose of nominating a successor, declared with one voice that the man most worthy of the sovereign power was Diocletian, who, having accepted the preferred dignity, signalized his accession by slaying with his own hands Arrius Aper praefect of the praetorians, who was arraigned of the murder of the deceased prince, his son-in-law [NUMERIANUS]. The proceedings upon this occasion were characterised by an intemperate haste, which gave plausibility to the report, that the avenger of Numerian, notwithstanding his solemn protestations of innocence and disinterested zeal, was less eager to satisfy the demands of justice than to avert suspicion from himself and to remove a formidable rival, especially since he did not scruple to confess that he had long anxiously sought to fulfil a prophecy delivered to him in early youth by a Gaulish Druidess, that he should mount a throne as soon as he had slain the wild-boar (Aper). These events took place in the course of the year 284, known in chronology as the era of Diocletian, or the era of the martyrs, an epoch long employed in the calculations of ecclesiastical writers, and still in use among Coptic Christians. After the ceremonies of installation had been completed at Nicomedeia, it became necessary to take the field forthwith against Carinus, who was hastening towards Asia at the head of a numerous and well-disciplined army. The opposing armies met near Margus in upper Moesia, and, after an obstinate struggle, victory declared for the hardy veterans of the Western legions; but while Carinus was hotly pursuing the flying foe he was slain by his own officers [CARINUS]. His troops, left without a leader, fraternized with their late enemies, Diocletian was acknowledged by the conjoined armies, and no one appeared prepared to dispute his claims. The conqueror used his victory with praiseworthy and politic moderation. There were no proscriptions, no confiscations, no banishments. Nearly the whole of the ministers and attendants of the deceased monarch were permitted to retain their offices, and even the praetorian praefect Aristobulus was continued in his command. There was little prospect, however, of a peaceful reign. In addition to the insubordinate spirit which prevailed universally among the soldiery, who had been accustomed for a long series of years to create and dethrone their rulers according to the suggestions of interest, passion, or caprice, the empire was threatened in the West by a formidable insurrection of the Bagaudae under Aelianus and Amandus [AELIANUS], in the East by the Persians, and in the North by the turbulent movements of the wild tribes upon the Danube. Feeling himself unable to cope single-handed with so many difficulties, Diocletian resolved to assume a colleague who should enjoy, nominally at least, equal rank and power with himself, and relieve him from the burden of undertaking in person distant wars. His choice fell upon the brave and experienced, but rough and unlettered soldier Maximianus [Maximianus Herculius], whom he invested with the title of Augustus, at Nicomedeia, in 286. At the same time the associated rulers adopted respectively the epithets of Jovius and Herculius, either from some superstitious motive, or, according to the explanation of one of the panegyrists, in order to declare to the world that while the elder possessed supreme wisdom to devise and direct, the younger could exert irresistible might in the execution of all projects.

The new emperor hastened to quell, by his presence, the disturbances in Gaul, and succeeded without difficulty in chastising the rebellious boors. But this achievement was but a poor consolation for the loss of Britain, and the glory of the two Augusti was dimmed by their forced acquiescence in the insolent usurpation of Carausius. [CARAUSIUS.]

Meanwhile, dangers which threatened the very existence of the Roman dominion became daily more imminent. The Egyptians, ever factious, had now risen in open insurrection, and their leader, Achilleus, had made himself master of Alexandria; the savage Blemmyes were ravaging the upper valley of the Nile; Julianus had assumed imperial ornaments at Carthage; a confederacy of five rude but warlike clans of Atlas, known as the (or Quinquegentiani), was spreading terror throughout the more peaceful districts of Africa; Tiridates, again expelled from Armenia, had been compelled once more to seek refuge in the Roman court; and Narses having crossed the Tigris, had recovered Mesopotamia, and openly announced his determination to re-unite all Asia under the sway of Persia; while the Germans, Goths, and Sarmatians were ready to pour down upon any unguarded point of the long line of frontier stretching from the mouths of the Rhine to the Euxine. In this emergency, in order that a vigorous resistance might be opposed to these numerous and formidable attacks in quarters of the world so distant from each other, and that the loyalty of the generals commanding all the great armies might be firmly secured, Diocletian resolved to introduce a new system of government. It was determined that, in addition to the two Augusti, there should be two Caesars also, that the whole empire should be divided among these four potentates, a certain fixed and definite portion being assigned to each, within which, in the absence of the rest, his jurisdiction should be absolute. All, however, being considered as colleagues working together for the accomplishment of the same object, the decrees of one were to be binding upon the rest; and while each Caesar was, in a certain degree, subordinate to the Augusti, the three junior members of this mighty partnership were required distinctly to recognise Diocletian as the head and guide of the whole. Accordingly, on the 1st of March 292, Constantius Chlorus and Galerius were proclaimed Caesars at Nicomedeia, and to knit more firmly the connecting bonds, they were both called upon to repudiate their wives; upon which the former received in marriage Theodora, the step-daughter of Maximian; the latter Valeria, the daughter of Diocletian. In the partition of the provinces the two younger princes were appointed to the posts of greatest labour and hazard. To Constantius were assigned Britain, Gaul, and Spain, the chief seat of government being fixed at Treves; to Galerius were intrusted Illyricum, and the whole line of the Danube, with Sirmium for a capital; Maximian resided at Milan, as governor of Italy and Africa, together with Sicily and the islands of the Tyrrhenian Sea; while Diocletian retained Thrace. Egypt, Syria, and Asia in his own hands, and established his court at Nicomedeia. The immediate results of this arrangement were most auspicious. Maximianus routed the Mauritanian hordes, and drove them back to their mountain fastnesses. while Julian being defeated perished by his own hands; Diocletian invested Alexandria, which was captured after a siege of eight months, and many thousands of the seditious citizens were slain, Busiris and Coptos were levelled with the ground, and all Egypt, struck with terror by the success and severity of the emperor, sank into abject submission. In Gaul an invading host of the Alemanni was repulsed with great slaughter after an obstinate resistance, Boulogne, the naval arsenal of Carausius, was forced to surrender, and the usurper having soon after been murdered by his chosen friend and minister, Allectus, the troops of Constantius effected a landing in Britain in two divisions, and the whole island was speedily recovered, after it had been dismembered from the empire for a space of nearly ten years. In the East the struggle was more severe; but the victory, although deferred for a while, was even more complete and more glorious. Galerius, who had quitted his own province to prosecute this war, sustained in his first campaign, a terrible defeat in the plains of Carrhae. The shattered army, however, was speedily recruited by large drafts from the veterans of Illyria, Moesiaand Dacia, and the Roman general, taught caution by experience, advanced warily through the mountains of Armenia, carefully avoiding the open country where cavalryy might act with advantage. Persevering steadily in this course, he at length, with 25,000 men, fell unexpectedly upon the careless and confident foe. They were completely routed, and the harem of Narses, who commanded in person and escaped with great difficulty, fell into the hands of the conquerors. The full fruits of this victory were secured by the wise policy of Diocletian, who resolved to seize the opportunity of offering a peace by which he might receive a moderate but certain advantage. A treaty was concluded, by which the independence of Armenia was guaranteed, and all Mesopotamia, together with five provinces beyond the Tigris and the command of the defiles of Caucasus, were ceded to the Romans. For forty years the conditions of this compact were observed with good faith, and the repose of the East remained undisturbed.

The long series of brilliant achievements, by which the barbarians had been driven back from every frontier, were completed when Diocletian entered upon the twentieth year of his reign, and the games common at each decennial period were combined with a triumph the most gorgeous which Rome had witnessed since the days of Aurelian.

But neither the mind nor the body of Diocletian, who was now fifty-nine years old, was able any longer to support the unceasing anxiety and toil to which he was exposed. On his journey to Nicomedeia he was attacked by an illness, from which, after protracted suffering, he scarcely escaped with life, and, even when immediate danger was past, found himself so exhausted and depressed, that he resolved to abdicate the purple. This resolution seems to have been soon formed, and it was speedily executed. On the 1st of May, A. D. 305, in a plain three miles from the city where he had first assumed the purple, in the presence of the army and the people, he solemnly divested himself of his royal robes. A similar scene was enacted on the same day at Milan by his reluctant colleague. Constantius Chlorus and Galerius being now, according to the principles of the new constitution, raised to the dignity of Augusti, Flavius Severus and Maximinus Daza were created Caesars. Diocletian returned to his native Dalmatia, and passed the remaining eight years of his life near Salona in philosophic retirement, devoted to rural pleasures and the cultivation of his garden. Aurelius Victor has preserved the well-known anecdote, that when solicited at a subsequent period, by the ambitious and discontented Maximian, to resume the honours which he had voluntarily resigned, his reply was, " Would you could see the vegetables planted by my hands at Salona, you would then never think of urging such an attempt." His death took place at the age of sixty-seven. The story in the Epitome of Victor, that he put himself to death in order to escape the violence which he apprehended from Constantine and Licinius, seems to be unsupported by external evidence or internal probability.

Although little doubt can be entertained with regard to the general accuracy of the leading facts enumerated in the above outline, the greatest confusion and embarrassment prevail with regard to the more minute details of this reign and the chronological arrangement of the events. Medals afford little or no aid, the biographies of the Augustan historians end with Carinus, no contemporary record has been preserved, and those portions of Ammianus Marcellinus and Zosimus which must have been devoted to this epoch have disappeared from their works, purposely omitted or destroyed, as some have imagined, by Christian transcribers, who were determined if possible to prevent any flattering picture of their persecutor or any chronicle of his glories from being transmitted to posterity. Hence we are thrown entirely upon the meagre and unsatisfactory compendiums of Eutropius, the Victors, and Festus; the vague and lying hyperboles of the panegyrists, and the avowedly hostile declamations of the author of the work, De Mortibus Persecutorum [CAECILIUS], and other writers of the same stamp. Hence, from sources so scanty and so impure, it is extremely difficult to derive such knowledge as may enable us to form a just conception of the real character of this remarkable man.

It is certain that he revolutionized the whole political system of the empire, and introduced a scheme of government, afterwards fully carried out and perfected by Constantine, as much at variance with that pursued by his predecessors as the power exercised by Octavianus and those who followed him differed from the authority of the constitutional magistrates of the republic. The object of this new and important change, and the means by which it was sought to attain that object, may be explained in a few words. The grand object was to protect the person of the sovereign from violence, and to insure a regular legitimate succession, thus putting an end to the rebellions and civil wars, by which the world had been torn to pieces ever since the extinction, in Nero, of the Julian blood. To accomplish what was sought, it was necessary to guard against insubordination among the powerful bodies of troops maintained on the more exposed frontiers, against mutiny among the praetorians at home, and against the faint spark of free and independent feeling among the senate and populace of Rome. Little was to be apprehended from the soldiery at a distance, unless led on by some favourite general; hence, by placing at the head of the four great armies four commanders all directly interested in preserving the existing order of things, it was believed that one great source of danger was removed, while two of these being marked out as heirs apparent to the throne long before their actual accession, it seemed probable that on the death of the Augusti they would advance to the higher grade as a matter of course, without question or commotion, their places being supplied by two new Caesars. Jealousies might undoubtedly arise, but these were guarded against by rendering each of the four jurisdictions as distinct and absolute as possible, while it was imagined that an attempt on the part of any one member of the confederacy to render himself supreme, would certainly be checked at once by the cordial combination of the remaining three, in self-defence. It was resolved to treat the praetorians with little ceremony; but, to prevent any outbreak, which despair might have rendered formidable, they were gradually dispersed, and then deprived of their privileges, while their former duties were discharged by the Jovian and Herculian battalions from Illyria, who were firm in their allegiance to their native princes. The degradation of Rome by the removal of the court, and the creation of four new capitals, was a death-blow to the influence of the Senate, and led quickly to the destruction of all old patriotic associations. Nor was less care and forethought bestowed on matters apparently trivial. The robe of cloth of gold, the slippers of silk dyed in purple, and embroidered with gems, the regal diadem wreathed around the brow, the titles of Lord and Master and God, the lowly prostrations, and the thousand intricacies of complicated etiquette which fenced round the imperial presence, were all attributed by short-sighted observers to the insolent pride of a Dalmatian slave intoxicated with unlooked-for prosperity, but were in reality part and parcel of a sagacious and well meditated plan, which sought to encircle the person of the sovereign with a sort of sacred and mysterious grandeur.

Passing over the military skill of Diocletian, we can scarcely refuse to acknowledge that the man who formed the scheme of reconstructing a great empire, and executed his plan within so brief a space of time, must have combined a bold and capacious intellect with singular prudence and practical dexterity. That his plans were such as a profound statesman would approve may fairly be questioned, for it needed but little knowledge of human nature to foresee, that the ingenious but complicated machine would never work with smoothness after the regulating hand of the inventor was withdrawn; and, accordingly, his death was the signal for a succession of furious struggles among the rival Caesars and Augusti, which did not terminate until the whole empire was reunited under Constantine. Still the great social change was accomplished; a new order of things was introduced which determined the relation between the sovereign and the subject, until the final downfall of the Roman sway, upon principles not before recognized in the Western world, and which to this day exercise no small influence upon the political condition of Europe.

One of the worst effects, in the first instance, of the revolution, was the vast increase of the public expenditure, caused by the necessity of supporting two imperial and two vice-regal courts upon a scale of oriental splendour, and by the magnificent edifices reared by the vanity or policy of the different rulers for the embellishment of their capitals or favourite residences. The amount of revenue required could be raised only by increased taxation, and we find that all classes of the community complained bitterly of the merciless exactions to which they were exposed. Yet, on the whole, Diocletian was by no means indifferent to the comfort and prosperity of his people. Various monopolies were abolished, trade was encouraged, a disposition was manifested to advance merit and to repress corruption in every department. The views entertained upon subjects connected with political economy are well illustrated by the singular edict lately discovered at Stratoniceia, by Colonel Leake, fixing the wages of labourers and artizans, together with the maximum price, throughout the world, of all the necessaries and commodities of life. It is not possible to avoid being struck by the change wrought upon the general aspect of public affairs during the years, not many in number, which elapsed between the accession and abdication of Diocletian. He found the empire weak and shattered, threatened with immediate dissolution, from intestine discord and external violence. He left it strong and compact, at peace within, and triumphant abroad, stretching from the Tigris to the Nile, from the shores of Holland to the Euxine.

By far the worst feature of this reign was the terrible persecution of the Christians. The conduct of the prince upon this occasion is the more remarkable, because we are at first sight unable to detect any motive which could have induced him to permit such atrocities, and one of the most marked features in his character was his earnest avoidance of harsh measures. The history of the affair seems briefly this : The pagans of the old school had formed a close alliance with the sceptical philosophers, and both perceived that the time was now arrived for a desperate struggle which must finally establish or destroy their supremacy. This faction found an organ in the relentless Galerius, stimulated partly by his own passions, but especially by the fanaticism of his mother, who was notorious for her devotion to some of the wildest and most revolting rites of Eastern superstition. As the health of Diocletian declined, his mind sunk in some degree under the pressure of disease, while the influence of his associate Augustus became every day more strong. At length, after repeated and most urgent representations, Galerius succeeded in extorting from his colleague--for even the most hostile accounts admit that the consent of Diocletian was given with the greatest reluctance--the first edict which, although stern and tyrannical in its ordinances, positively forbad all personal violence. But when the proclamation was torn down by an indignant believer, and when this act of contumacy was followed by a conflagration in the palace, occurring under the most suspicious circumstances, and unhesitatingly ascribed by Galerius to the Christians, the emperor considered that the grand principle for which he had been so strenuously contending, the supreme majesty and inviolability of the royal person, was openly assailed, and thus was persuaded without further resistance to give his assent to those sanguinary decrees which for years deluged the world with innocent blood. It is not improbable that the intellects of Diocletian were seriously affected, and that his malady may have amounted to absolute insanity. (Aurel. Victor. de Cacs. 39, Epit. 39; Eutrop. 9.13. &c.; Zonar. 12.31.)