The plain of Mardia in Thrace was the theatre of a second battle no less obstinate and bloody than the former. The troops on both sides displayed the same valor and discipline; and the victory was once more decided by the superior abilities of Constantine, who directed a body of five thousand men to gain an advantageous height, from whence, during the heat of the action, they attacked the rear of the enemy, and made a very considerable slaughter. The troops of Licinius, however, presenting a double front, still maintained their ground, till the approach of night put an end to the combat, and secured their retreat towards the mountains of Macedonia. The loss of two battles, and of his bravest veterans, reduced the fierce spirit of Licinius to sue for peace. His ambassador Mistrianus was admitted to the audience of Constantine: he expatiated on the common topics of moderation and humanity, which are so familiar to the eloquence of the vanquished; represented in the most insinuating language, that the event of the war was still doubtful, whilst its inevitable calamities were alike pernicious to both the contending parties; and declared that he was authorized to propose a lasting and honorable peace in the name of the two emperors his masters. Constantine received the mention of Valens with indignation and contempt. "It was not for such a purpose," he sternly replied, "that we have advanced from the shores of the western ocean in an uninterrupted course of combats and victories, that, after rejecting an ungrateful kinsman, we should accept for our colleague a contemptible slave. The abdication of Valens is the first article of the treaty." It was necessary to accept this humiliating condition; and the unhappy Valens, after a reign of a few days, was deprived of the purple and of his life. As soon as this obstacle was removed, the tranquillity of the Roman world was easily restored. The successive defeats of Licinius had ruined his forces, but they had displayed his courage and abilities. His situation was almost desperate, but the efforts of despair are sometimes formidable, and the good sense of Constantine preferred a great and certain advantage to a third trial of the chance of arms. He consented to leave his rival, or, as he again styled Licinius, his friend and brother, in the possession of Thrace, Asia Minor, Syria, and Egypt; but the provinces of Pannonia, Dalmatia, Dacia, Macedonia, and Greece, were yielded to the Western empire, and the dominions of Constantine now extended from the confines of Caledonia to the extremity of Peloponnesus. It was stipulated by the same treaty, that three royal youths, the sons of emperors, should be called to the hopes of the succession. Crispus and the young Constantine were soon afterwards declared Cæsars in the West, while the younger Licinius was invested with the same dignity in the East. In this double proportion of honors, the conqueror asserted the superiority of his arms and power.
The reconciliation of Constantine and Licinius, though it was imbittered by resentment and jealousy, by the remembrance of recent injuries, and by the apprehension of future dangers, maintained, however, above eight years, the tranquility of the Roman world. As a very regular series of the Imperial laws commences about this period, it would not be difficult to transcribe the civil regulations which employed the leisure of Constantine. But the most important of his institutions are intimately connected with the new system of policy and religion, which was not perfectly established till the last and peaceful years of his reign. There are many of his laws, which, as far as they concern the rights and property of individuals, and the practice of the bar, are more properly referred to the private than to the public jurisprudence of the empire; and he published many edicts of so local and temporary a nature, that they would ill deserve the notice of a general history. Two laws, however, may be selected from the crowd; the one for its importance, the other for its singularity; the former for its remarkable benevolence, the latter for its excessive severity. 1. The horrid practice, so familiar to the ancients, of exposing or murdering their new-born infants, was become every day more frequent in the provinces, and especially in Italy. It was the effect of distress; and the distress was principally occasioned by the intolerant burden of taxes, and by the vexatious as well as cruel prosecutions of the officers of the revenue against their insolvent debtors. The less opulent or less industrious part of mankind, instead of rejoicing in an increase of family, deemed it an act of paternal tenderness to release their children from the impending miseries of a life which they themselves were unable to support. The humanity of Constantine; moved, perhaps, by some recent and extraordinary instances of despair, * engaged him to address an edict to all the cities of Italy, and afterwards of Africa, directing immediate and sufficient relief to be given to those parents who should produce before the magistrates the children whom their own poverty would not allow them to educate. But the promise was too liberal, and the provision too vague, to effect any general or permanent benefit. The law, though it may merit some praise, served rather to display than to alleviate the public distress. It still remains an authentic monument to contradict and confound those venal orators, who were too well satisfied with their own situation to discover either vice or misery under the government of a generous sovereign. 2. The laws of Constantine against rapes were dictated with very little indulgence for the most amiable weaknesses of human nature; since the description of that crime was applied not only to the brutal violence which compelled, but even to the gentle seduction which might persuade, an unmarried woman, under the age of twenty-five, to leave the house of her parents. "The successful ravisher was punished with death; and as if simple death was inadequate to the enormity of his guilt, he was either burnt alive, or torn in pieces by wild beasts in the amphitheatre. The virgin's declaration, that she had been carried away with her own consent, instead of saving her lover, exposed her to share his fate. The duty of a public prosecution was intrusted to the parents of the guilty or unfortunate maid; and if the sentiments of nature prevailed on them to dissemble the injury, and to repair by a subsequent marriage the honor of their family, they were themselves punished by exile and confiscation. The slaves, whether male or female, who were convicted of having been accessory to rape or seduction, were burnt alive, or put to death by the ingenious torture of pouring down their throats a quantity of melted lead. As the crime was of a public kind, the accusation was permitted even to strangers. The commencement of the action was not limited to any term of years, and the consequences of the sentence were extended to the innocent offspring of such an irregular union." But whenever the offence inspires less horror than the punishment, the rigor of penal law is obliged to give way to the common feelings of mankind. The most odious parts of this edict were softened or repealed in the subsequent reigns; and even Constantine himself very frequently alleviated, by partial acts of mercy, the stern temper of his general institutions. Such, indeed, was the singular humor of that emperor, who showed himself as indulgent, and even remiss, in the execution of his laws, as he was severe, and even cruel, in the enacting of them. It is scarcely possible to observe a more decisive symptom of weakness, either in the character of the prince, or in the constitution of the government.
The civil administration was sometimes interrupted by the military defence of the empire. Crispus, a youth of the most amiable character, who had received with the title of Cæsar the command of the Rhine, distinguished his conduct, as well as valor, in several victories over the Franks and Alemanni, and taught the barbarians of that frontier to dread the eldest son of Constantine, and the grandson of Constantius. The emperor himself had assumed the more difficult and important province of the Danube. The Goths, who in the time of Claudius and Aurelian had felt the weight of the Roman arms, respected the power of the empire, even in the midst of its intestine divisions. But the strength of that warlike nation was now restored by a peace of near fifty years; a new generation had arisen, who no longer remembered the misfortunes of ancient days; the Sarmatians of the Lake Mæotis followed the Gothic standard either as subjects or as allies, and their united force was poured upon the countries of Illyricum. Campona, Margus, and Benonia, appear to have been the scenes of several memorable sieges and battles; and though Constantine encountered a very obstinate resistance, he prevailed at length in the contest, and the Goths were compelled to purchased an ignominious retreat, by restoring the booty and prisoners which they had taken. Nor was this advantage sufficient to satisfy the indignation of the emperor. He resolved to chastise as well as to repulse the insolent barbarians who had dared to invade the territories of Rome. At the head of his legions he passed the Danube after repairing the bridge which had been constructed by Trajan, penetrated into the strongest recesses of Dacia, and when he had inflicted a severe revenge, condescended to give peace to the suppliant Goths, on condition that, as often as they were required, they should supply his armies with a body of forty thousand soldiers. Exploits like these were no doubt honorable to Constantine, and beneficial to the state; but it may surely be questioned, whether they can justify the exaggerated assertion of Eusebius, that all Scythia, as far as the extremity of the North, divided as it was into so many names and nations of the most various and savage manners, had been added by his victorious arms to the Roman empire.
In this exalted state of glory, it was impossible that Constantine should any longer endure a partner in the empire. Confiding in the superiority of his genius and military power, he determined, without any previous injury, to exert them for the destruction of Licinius, whose advanced age and unpopular vices seemed to offer a very easy conquest. But the old emperor, awakened by the approaching danger, deceived the expectations of his friends, as well as of his enemies. Calling forth that spirit and those abilities by which he had deserved the friendship of Galerius and the Imperial purple, he prepared himself for the contest, collected the forces of the East, and soon filled the plains of Hadrianople with his troops, and the Straits of the Hellespont with his fleet. The army consisted of one hundred and fifty thousand foot, and fifteen thousand horse; and as the cavalry was drawn, for the most part, from Phrygia and Cappadocia, we may conceive a more favorable opinion of the beauty of the horses, than of the courage and dexterity of their riders. The fleet was composed of three hundred and fifty galleys of three ranks of oars. A hundred and thirty of these were furnished by Egypt and the adjacent coast of Africa. A hundred and ten sailed from the ports of Phoenicia and the Isle of Cyprus; and the maritime countries of Bithynia, Ionia, and Caria, were likewise obliged to provide a hundred and ten galleys. The troops of Constantine were ordered to a rendezvous at Thessalonica; they amounted to above a hundred and twenty thousand horse and foot. Their emperor was satisfied with their martial appearance, and his army contained more soldiers, though fewer men, than that of his eastern competitor. The legions of Constantine were levied in the warlike provinces of Europe; action had confirmed their discipline, victory had elevated their hopes, and there were among them a great number of veterans, who, after seventeen glorious campaigns under the same leader, prepared themselves to deserve an honorable dismission by a last effort of their valor. But the naval preparations of Constantine were in every respect much inferior to those of Licinius. The maritime cities of Greece sent their respective quotas of men and ships to the celebrated harbor of Piræus, and their united forces consisted of no more than two hundred small vessels -- a very feeble armament, if it is compared with those formidable fleets which were equipped and maintained by the republic of Athens during the Peloponnesian war. Since Italy was no longer the seat of government, the naval establishments of Misenum and Ravenna had been gradually neglected; and as the shipping and mariners of the empire were supported by commerce rather than by war, it was natural that they should the most abound in the industrious provinces of Egypt and Asia. It is only surprising that the eastern emperor, who possessed so great a superiority at sea, should have neglected the opportunity of carrying an offensive war into the centre of his rival's dominions.
Instead of embracing such an active resolution, which might have changed the whole face of the war, the prudent Licinius expected the approach of his rival in a camp near Hadrianople, which he had fortified with an anxious care, that betrayed his apprehension of the event. Constantine directed his march from Thessalonica towards that part of Thrace, till he found himself stopped by the broad and rapid stream of the Hebrus, and discovered the numerous army of Licinius, which filled the steep ascent of the hill, from the river to the city of Hadrianople. Many days were spent in doubtful and distant skirmishes; but at length the obstacles of the passage and of the attack were removed by the intrepid conduct of Constantine. In this place we might relate a wonderful exploit of Constantine, which, though it can scarcely be paralleled either in poetry or romance, is celebrated, not by a venal orator devoted to his fortune, but by an historian, the partial enemy of his fame. We are assured that the valiant emperor threw himself into the River Hebrus, accompanied only by twelve horsemen, and that by the effort or terror of his invincible arm, he broke, slaughtered, and put to flight a host of a hundred and fifty thousand men. The credulity of Zosimus prevailed so strongly over his passion, that among the events of the memorable battle of Hadrianople, he seems to have selected and embellished, not the most important, but the most marvellous. The valor and danger of Constantine are attested by a slight wound which he received in the thigh; but it may be discovered even from an imperfect narration, and perhaps a corrupted text, that the victory was obtained no less by the conduct of the general than by the courage of the hero; that a body of five thousand archers marched round to occupy a thick wood in the rear of the enemy, whose attention was diverted by the construction of a bridge, and that Licinius, perplexed by so many artful evolutions, was reluctantly drawn from his advantageous post to combat on equal ground on the plain. The contest was no longer equal. His confused multitude of new levies was easily vanquished by the experienced veterans of the West. Thirty-four thousand men are reported to have been slain. The fortified camp of Licinius was taken by assault the evening of the battle; the greater part of the fugitives, who had retired to the mountains, surrendered themselves the next day to the discretion of the conqueror; and his rival, who could no longer keep the field, confined himself within the walls of Byzantium.
The siege of Byzantium, which was immediately undertaken by Constantine, was attended with great labor and uncertainty. In the late civil wars, the fortifications of that place, so justly considered as the key of Europe and Asia, had been repaired and strengthened; and as long as Licinius remained master of the sea, the garrison was much less exposed to the danger of famine than the army of the besiegers. The naval commanders of Constantine were summoned to his camp, and received his positive orders to force the passage of the Hellespont, as the fleet of Licinius, instead of seeking and destroying their feeble enemy, continued inactive in those narrow straits, where its superiority of numbers was of little use or advantage. Crispus, the emperor's eldest son, was intrusted with the execution of this daring enterprise, which he performed with so much courage and success, that he deserved the esteem, and most probably excited the jealousy, of his father. The engagement lasted two days; and in the evening of the first, the contending fleets, after a considerable and mutual loss, retired into their respective harbors of Europe and Asia. The second day, about noon, a strong south wind sprang up, which carried the vessels of Crispus against the enemy; and as the casual advantage was improved by his skilful intrepidity, he soon obtained a complete victory. A hundred and thirty vessels were destroyed, five thousand men were slain, and Amandus, the admiral of the Asiatic fleet, escaped with the utmost difficulty to the shores of Chalcedon. As soon as the Hellespont was open, a plentiful convoy of provisions flowed into the camp of Constantine, who had already advanced the operations of the siege. He constructed artificial mounds of earth of an equal height with the ramparts of Byzantium. The lofty towers which were erected on that foundation galled the besieged with large stones and darts from the military engines, and the battering rams had shaken the walls in several places. If Licinius persisted much longer in the defence, he exposed himself to be involved in the ruin of the place. Before he was surrounded, he prudently removed his person and treasures to Chalcedon in Asia; and as he was always desirous of associating companions to the hopes and dangers of his fortune, he now bestowed the title of Cæsar on Martinianus, who exercised one of the most important offices of the empire.
Such were still the resources, and such the abilities, of Licinius, that, after so many successive defeats, he collected in Bithynia a new army of fifty or sixty thousand men, while the activity of Constantine was employed in the siege of Byzantium. The vigilant emperor did not, however, neglect the last struggles of his antagonist. A considerable part of his victorious army was transported over the Bosphorus in small vessels, and the decisive engagement was fought soon after their landing on the heights of Chrysopolis, or, as it is now called, of Scutari. The troops of Licinius, though they were lately raised, ill armed, and worse disciplined, made head against their conquerors with fruitless but desperate valor, till a total defeat, and a slaughter of five and twenty thousand men, irretrievably determined the fate of their leader. He retired to Nicomedia, rather with the view of gaining some time for negotiation, than with the hope of any effectual defence. Constantia, his wife, and the sister of Constantine, interceded with her brother in favor of her husband, and obtained from his policy, rather than from his compassion, a solemn promise, confirmed by an oath, that after the sacrifice of Martinianus, and the resignation of the purple, Licinius himself should be permitted to pass the remainder of this life in peace and affluence. The behavior of Constantia, and her relation to the contending parties, naturally recalls the remembrance of that virtuous matron who was the sister of Augustus, and the wife of Antony. But the temper of mankind was altered, and it was no longer esteemed infamous for a Roman to survive his honor and independence. Licinius solicited and accepted the pardon of his offences, laid himself and his purple at the feet of his lord and master, was raised from the ground with insulting pity, was admitted the same day to the Imperial banquet, and soon afterwards was sent away to Thessalonica, which had been chosen for the place of his confinement. His confinement was soon terminated by death, and it is doubtful whether a tumult of the soldiers, or a decree of the senate, was suggested as the motive for his execution. According to the rules of tyranny, he was accused of forming a conspiracy, and of holding a treasonable correspondence with the barbarians; but as he was never convicted, either by his own conduct or by any legal evidence, we may perhaps be allowed, from his weakness, to presume his innocence. The memory of Licinius was branded with infamy, his statues were thrown down, and by a hasty edict, of such mischievous tendency that it was almost immediately corrected, all his laws, and all the judicial proceedings of his reign, were at once abolished. By this victory of Constantine, the Roman world was again united under the authority of one emperor, thirty-seven years after Diocletian had divided his power and provinces with his associate Maximian.
The successive steps of the elevation of Constantine, from his first assuming the purple at York, to the resignation of Licinius, at Nicomedia, have been related with some minuteness and precision, not only as the events are in themselves both interesting and important, but still more, as they contributed to the decline of the empire by the expense of blood and treasure, and by the perpetual increase, as well of the taxes, as of the military establishment. The foundation of Constantinople, and the establishment of the Christian religion, were the immediate and memorable consequences of this revolution.