Britain had none but domestic enemies to dread; and as long as the governors preserved their fidelity, and the troops their discipline, the incursions of the naked savages of Scotland or Ireland could never materially affect the safety of the province. The peace of the continent, and the defence of the principal rivers which bounded the empire, were objects of far greater difficulty and importance. The policy of Diocletian, which inspired the councils of his associates, provided for the public tranquility, by encouraging a spirit of dissension among the barbarians, and by strengthening the fortifications of the Roman limit. In the East he fixed a line of camps from Egypt to the Persian dominions, and for every camp, he instituted an adequate number of stationary troops, commanded by their respective officers, and supplied with every kind of arms, from the new arsenals which he had formed at Antioch, Emesa, and Damascus. Nor was the precaution of the emperor less watchful against the well-known valor of the barbarians of Europe. From the mouth of the Rhine to that of the Danube, the ancient camps, towns, and citidels, were diligently reestablished, and, in the most exposed places, new ones were skilfully constructed: the strictest vigilance was introduced among the garrisons of the frontier, and every expedient was practised that could render the long chain of fortifications firm and impenetrable. A barrier so respectable was seldom violated, and the barbarians often turned against each other their disappointed rage. The Goths, the Vandals, the Gepidæ, the Burgundians, the Alemanni, wasted each other's strength by destructive hostilities: and whosoever vanquished, they vanquished the enemies of Rome. The subjects of Diocletian enjoyed the bloody spectacle, and congratulated each other, that the mischiefs of civil war were now experienced only by the barbarians.
Notwithstanding the policy of Diocletian, it was impossible to maintain an equal and undisturbed tranquillity during a reign of twenty years, and along a frontier of many hundred miles. Sometimes the barbarians suspended their domestic animosities, and the relaxed vigilance of the garrisons sometimes gave a passage to their strength or dexterity. Whenever the provinces were invaded, Diocletian conducted himself with that calm dignity which he always affected or possessed; reserved his presence for such occasions as were worthy of his interposition, never exposed his person or reputation to any unnecessary danger, insured his success by every means that prudence could suggest, and displayed, with ostentation, the consequences of his victory. In wars of a more difficult nature, and more doubtful event, he employed the rough valor of Maximian; and that faithful soldier was content to ascribe his own victories to the wise counsels and auspicious influence of his benefactor. But after the adoption of the two Cæsars, the emperors themselves, retiring to a less laborious scene of action, devolved on their adopted sons the defence of the Danube and of the Rhine. The vigilant Galerius was never reduced to the necessity of vanquishing an army of barbarians on the Roman territory. The brave and active Contsantius delivered Gaul from a very furious inroad of the Alemanni; and his victories of Langres and Vindonissa appear to have been actions of considerable danger and merit. As he traversed the open country with a feeble guard, he was encompassed on a sudden by the superior multitude of the enemy. He retreated with difficulty towards Langres; but, in the general consternation, the citizens refused to open their gates, and the wounded prince was drawn up the wall by the means of a rope. But, on the news of his distress, the Roman troops hastened from all sides to his relief, and before the evening he had satisfied his honor and revenge by the slaughter of six thousand Alemanni. From the monuments of those times, the obscure traces of several other victories over the barbarians of Sarmatia and Germany might possibly be collected; but the tedious search would not be rewarded either with amusement or with instruction.
The conduct which the emperor Probus had adopted in the disposal of the vanquished, was imitated by Diocletian and his associates. The captive barbarians, exchanging death for slavery, were distributed among the provincials, and assigned to those districts (in Gaul, the territories of Amiens, Beauvais, Cambray, Treves, Langres, and Troyes, are particularly specified ) which had been depopulated by the calamities of war. They were usefully employed as shepherds and husbandmen, but were denied the exercise of arms, except when it was found expedient to enroll them in the military service. Nor did the emperors refuse the property of lands, with a less servile tenure, to such of the barbarians as solicited the protection of Rome. They granted a settlement to several colonies of the Carpi, the Bastarnæ, and the Sarmatians; and, by a dangerous indulgence, permitted them in some measure to retain their national manners and independence. Among the provincials, it was a subject of flattering exultation, that the barbarian, so lately an object of terror, now cultivated their lands, drove their cattle to the neighboring fair, and contributed by his labor to the public plenty. They congratulated their masters on the powerful accession of subjects and soldiers; but they forgot to observe, that multitudes of secret enemies, insolent from favor, or desperate from oppression, were introduced into the heart of the empire.
While the Cæsars exercised their valor on the banks of the Rhine and Danube, the presence of the emperors was required on the southern confines of the Roman world. From the Nile to Mount Atlas Africa was in arms. A confederacy of five Moorish nations issued from their deserts to invade the peaceful provinces. Julian had assumed the purple at Carthage. Achilleus at Alexandria, and even the Blemmyes, renewed, or rather continued, their incursions into the Upper Egypt. Scarcely any circumstances have been preserved of the exploits of Maximian in the western parts of Africa; but it appears, by the event, that the progress of his arms was rapid and decisive, that he vanquished the fiercest barbarians of Mauritania, and that he removed them from the mountains, whose inaccessible strength had inspired their inhabitants with a lawless confidence, and habituated them to a life of rapine and violence. Diocletian, on his side, opened the campaign in Egypt by the siege of Alexandria, cut off the aqueducts which conveyed the waters of the Nile into every quarter of that immense city, and rendering his camp impregnable to the sallies of the besieged multitude, he pushed his reiterated attacks with caution and vigor. After a siege of eight months, Alexandria, wasted by the sword and by fire, implored the clemency of the conqueror, but it experienced the full extent of his severity. Many thousands of the citizens perished in a promiscuous slaughter, and there were few obnoxious persons in Egypt who escaped a sentence either of death or at least of exile. The fate of Busiris and of Coptos was still more melancholy than that of Alexandria: those proud cities, the former distinguished by its antiquity, the latter enriched by the passage of the Indian trade, were utterly destroyed by the arms and by the severe order of Diocletian. The character of the Egyptian nation, insensible to kindness, but extremely susceptible of fear, could alone justify this excessive rigor. The seditions of Alexandria had often affected the tranquillity and subsistence of Rome itself. Since the usurpation of Firmus, the province of Upper Egypt, incessantly relapsing into rebellion, had embraced the alliance of the savages of Æthiopia. The number of the Blemmyes, scattered between the Island of Meroe and the Red Sea, was very inconsiderable, their disposition was unwarlike, their weapons rude and inoffensive. Yet in the public disorders, these barbarians, whom antiquity, shocked with the deformity of their figure, had almost excluded from the human species, presumed to rank themselves among the enemies of Rome. Such had been the unworthy allies of the Egyptians; and while the attention of the state was engaged in more serious wars, their vexations inroads might again harass the repose of the province. With a view of opposing to the Blemmyes a suitable adversary, Diocletian persuaded the Nobatæ, or people of Nubia, to remove from their ancient habitations in the deserts of Libya, and resigned to them an extensive but unprofitable territory above Syene and the cataracts of the Nile, with the stipulation, that they should ever respect and guard the frontier of the empire. The treaty long subsisted; and till the establishment of Christianity introduced stricter notions of religious worship, it was annually ratified by a solemn sacrifice in the Isle of Elephantine, in which the Romans, as well as the barbarians, adored the same visible or invisible powers of the universe.
At the same time that Diocletian chastised the past crimes of the Egyptians, he provided for their future safety and happiness by many wise regulations, which were confirmed and enforced under the succeeding reigns. One very remarkable edict which he published, instead of being condemned as the effect of jealous tyranny, deserves to be applauded as an act of prudence and humanity. He caused a diligent inquiry to be made "for all the ancient books which treated of the admirable art of making gold and silver, and without pity, committed them to the flames; apprehensive, as we are assumed, lest the opulence of the Egyptians should inspire them with confidence to rebel against the empire." But if Diocletian had been convinced of the reality of that valuable art, far from extinguishing the memory, he would have converted the operation of it to the benefit of the public revenue. It is much more likely, that his good sense discovered to him the folly of such magnificent pretensions, and that he was desirous of preserving the reason and fortunes of his subjects from the mischievous pursuit. It may be remarked, that these ancient books, so liberally ascribed to Pythagoras, to Solomon, or to Hermes, were the pious frauds of more recent adepts. The Greeks were inattentive either to the use or to the abuse of chemistry. In that immense register, where Pliny has deposited the discoveries, the arts, and the errors of mankind, there is not the least mention of the transmutation of metals; and the persecution of Diocletian is the first authentic event in the history of alchemy. The conquest of Egypt by the Arabs diffused that vain science over the globe. Congenial to the avarice of the human heart, it was studied in China as in Europe, with equal eagerness, and with equal success. The darkness of the middle ages insured a favorable reception to every tale of wonder, and the revival of learning gave new vigor to hope, and suggested more specious arts of deception. Philosophy, with the aid of experience, has at length banished the study of alchemy; and the present age, however desirous of riches, is content to seek them by the humbler means of commerce and industry.
The reduction of Egypt was immediately followed by the Persian war. It was reserved for the reign of Diocletian to vanquish that powerful nation, and to extort a confession from the successors of Artaxerxes, of the superior majesty of the Roman empire.
We have observed, under the reign of Valerian, that Armenia was subdued by the perfidy and the arms of the Persians, and that, after the assassination of Chosroes, his son Tiridates, the infant heir of the monarchy, was saved by the fidelity of his friends, and educated under the protection of the emperors. Tiridates derived from his exile such advantages as he could never have obtained on the throne of Armenia; the early knowledge of adversity, of mankind, and of the Roman discipline. He signalized his youth by deeds of valor, and displayed a matchless dexterity, as well as strength, in every martial exercise, and even in the less honorable contests of the Olympian games. Those qualities were more nobly exerted in the defence of his benefactor Licinius. That officer, in the sedition which occasioned the death of Probus, was exposed to the most imminent danger, and the enraged soldiers were forcing their way into his tent, when they were checked by the single arm of the Armenian prince. The gratitude of Tiridates contributed soon afterwards to his restoration. Licinius was in every station the friend and companion of Galerius, and the merit of Galerius, long before he was raised to the dignity of Cæsar, had been known and esteemed by Diocletian. In the third year of that emperor's reign Tiridates was invested with the kingdom of Armenia. The justice of the measure was not less evident than its expediency. It was time to rescue from the usurpation of the Persian monarch an important territory, which, since the reign of Nero, had been always granted under the protection of the empire to a younger branch of the house of Arsaces.
When Tiridates appeared on the frontiers of Armenia, he was received with an unfeigned transport of joy and loyalty. During twenty-six years, the country had experienced the real and imaginary hardships of a foreign yoke. The Persian monarchs adorned their new conquest with magnificent buildings; but those monuments had been erected at the expense of the people, and were abhorred as badges of slavery. The apprehension of a revolt had inspired the most rigorous precautions: oppression had been aggravated by insult, and the consciousness of the public hatred had been productive of every measure that could render it still more implacable. We have already remarked the intolerant spirit of the Magian religion. The statues of the deified kings of Armenia, and the sacred images of the sun and moon, were broke in pieces by the zeal of the conqueror; and the perpetual fire of Ormuzd was kindled and preserved upon an altar erected on the summit of Mount Bagavan. It was natural, that a people exasperated by so many injuries, should arm with zeal in the cause of their independence, their religion, and their hereditary sovereign. The torrent bore down every obstacle, and the Persian garrisons retreated before its fury. The nobles of Armenia flew to the standard of Tiridates, all alleging their past merit, offering their future service, and soliciting from the new king those honors and rewards from which they had been excluded with disdain under the foreign government. The command of the army was bestowed on Artavasdes, whose father had saved the infancy of Tiridates, and whose family had been massacred for that generous action. The brother of Artavasdes obtained the government of a province. One of the first military dignities was conferred on the satrap Otas, a man of singular temperance and fortitude, who presented to the king his sister and a considerable treasure, both of which, in a sequestered fortress, Otas had preserved from violation. Among the Armenian nobles appeared an ally, whose fortunes are too remarkable to pass unnoticed. His name was Mamgo, his origin was Scythian, and the horde which acknowledge his authority had encamped a very few years before on the skirts of the Chinese empire, which at that time extended as far as the neighborhood of Sogdiana. Having incurred the displeasure of his master, Mamgo, with his followers, retired to the banks of the Oxus, and implored the protection of Sapor. The emperor of China claimed the fugitive, and alleged the rights of sovereignty. The Persian monarch pleaded the laws of hospitality, and with some difficulty avoided a war, by the promise that he would banish Mamgo to the uttermost parts of the West, a punishment, as he described it, not less dreadful than death itself. Armenia was chosen for the place of exile, and a large district was assigned to the Scythian horde, on which they might feed their flocks and herds, and remove their encampment from one place to another, according to the different seasons of the year. They were employed to repel the invasion of Tiridates; but their leader, after weighing the obligations and injuries which he had received from the Persian monarch, resolved to abandon his party. The Armenian prince, who was well acquainted with this merit as well as power of Mamgo, treated him with distinguished respect; and, by admitting him into his confidence, acquired a brave and faithful servant, who contributed very effectually to his restoration.
For a while, fortune appeared to favor the enterprising valor of Tiridates. He not only expelled the enemies of his family and country from the whole extent of Armenia, but in the prosecution of his revenge he carried his arms, or at least his incursions, into the heart of Assyria. The historian, who has preserved the name of Tiridates from oblivion, celebrates, with a degree of national enthusiasm, his personal prowess: and, in the true spirit of eastern romance, describes the giants and the elephants that fell beneath his invincible arm. It is from other information that we discover the distracted state of the Persian monarchy, to which the king of Armenia was indebted for some part of his advantages. The throne was disputed by the ambition of contending brothers; and Hormuz, after exerting without success the strength of his own party, had recourse to the dangerous assistance of the barbarians who inhabited the banks of the Caspian Sea. The civil war was, however, soon terminated, either by a victor or by a reconciliation; and Narses, who was universally acknowledged as king of Persia, directed his whole force against the foreign enemy. The contest then became too unequal; nor was the valor of the hero able to withstand the power of the monarch, Tiridates, a second time expelled from the throne of Armenia, once more took refuge in the court of the emperors. * Narses soon reestablished his authority over the revolted province; and loudly complaining of the protection afforded by the Romans to rebels and fugitives, aspired to the conquest of the East.
Neither prudence nor honor could permit the emperors to forsake the cause of the Armenian king, and it was resolved to exert the force of the empire in the Persian war. Diocletian, with the calm dignity which he constantly assumed, fixed his own station in the city of Antioch, from whence he prepared and directed the military operations. The conduct of the legions was intrusted to the intrepid valor of Galerius, who, for that important purpose, was removed from the banks of the Danube to those of the Euphrates. The armies soon encountered each other in the plains of Mesopotamia, and two battles were fought with various and doubtful success; but the third engagement was of a more decisive nature; and the Roman army received a total overthrow, which is attributed to the rashness of Galerius, who, with an inconsiderable body of troops, attacked the innumerable host of the Persians. But the consideration of the country that was the scene of action, may suggest another reason for his defeat. The same ground on which Galerius was vanquished, had been rendered memorable by the death of Crassus, and the slaughter of ten legions. It was a plain of more than sixty miles, which extended from the hills of Carrhæ to the Euphrates; a smooth and barren surface of sandy desert, without a hillock, without a tree, and without a spring of fresh water. The steady infantry of the Romans, fainting with heat and thirst, could neither hope for victory if they preserved their ranks, nor break their ranks without exposing themselves to the most imminent danger. In this situation they were gradually encompassed by the superior numbers, harassed by the rapid evolutions, and destroyed by the arrows of the barbarian cavalry. The king of Armenia had signalized his valor in the battle, and acquired personal glory by the public misfortune. He was pursued as far as the Euphrates; his horse was wounded, and it appeared impossible for him to escape the victorious enemy. In this extremity Tiridates embraced the only refuge which appeared before him: he dismounted and plunged into the stream. His armor was heavy, the river very deep, and at those parts at least half a mile in breadth; yet such was his strength and dexterity, that he reached in safety the opposite bank. With regard to the Roman general, we are ignorant of the circumstances of his escape; but when he returned to Antioch, Diocletian received him, not with the tenderness of a friend and colleague, but with the indignation of an offended sovereign. The haughtiest of men, clothed in his purple, but humbled by the sense of his fault and misfortune, was obliged to follow the emperor's chariot above a mile on foot, and to exhibit, before the whole court, the spectacle of his disgrace.
As soon as Diocletian had indulged his private resentment, and asserted the majesty of supreme power, he yielded to the submissive entreaties of the Cæsar, and permitted him to retrieve his own honor, as well as that of the Roman arms. In the room of the unwarlike troops of Asia, which had most probably served in the first expedition, a second army was drawn from the veterans and new levies of the Illyrian frontier, and a considerable body of Gothic auxiliaries were taken into the Imperial pay. At the head of a chosen army of twenty-five thousand men, Galerius again passed the Euphrates; but, instead of exposing his legions in the open plains of Mesopotamia he advanced through the mountains of Armenia, where he found the inhabitants devoted to his cause, and the country as favorable to the operations of infantry as it was inconvenient for the motions of cavalry. Adversity had confirmed the Roman discipline, while the barbarians, elated by success, were become so negligent and remiss, that in the moment when they least expected it, they were surprised by the active conduct of Galerius, who, attended only by two horsemen, had with his own eyes secretly examined the state and position of their camp. A surprise, especially in the night time, was for the most part fatal to a Persian army. "Their horses were tied, and generally shackled, to prevent their running away; and if an alarm happened, a Persian had his housing to fix, his horse to bridle, and his corselet to put on, before he could mount." On this occasion, the impetuous attack of Galerius spread disorder and dismay over the camp of the barbarians. A slight resistance was followed by a dreadful carnage, and, in the general confusion, the wounded monarch (for Narses commanded his armies in person) fled towards the deserts of Media. His sumptuous tents, and those of his satraps, afforded an immense booty to the conqueror; and an incident is mentioned, which proves the rustic but martial ignorance of the legions in the elegant superfluities of life. A bag of shining leather, filled with pearls, fell into the hands of a private soldier; he carefully preserved the bag, but he threw away its contents, judging that whatever was of no use could not possibly be of any value. The principal loss of Narses was of a much more affecting nature. Several of his wives, his sisters, and children, who had attended the army, were made captives in the defeat. But though the character of Galerius had in general very little affinity with that of Alexander, he imitated, after his victory, the amiable behavior of the Macedonian towards the family of Darius. The wives and children of Narses were protected from violence and rapine, conveyed to a place of safety, and treated with every mark of respect and tenderness, that was due from a generous enemy to their age, their sex, and their royal dignity.