The Roman Empire reached its greatest extent under Marcus Ulpius Traianus, the fourteenth emperor. Of him it was said that he "built the world over," and the Romans themselves regarded him as the best, and perhaps the greatest of their emperors. He was a native of Italica, in Spain. The family to which he belonged was probably Italian, and not Iberian, by blood. His father began life as a common legionary soldier, and fought his way up to the consulship and the governorship of Asia. He was one of the hardest fighters in Judæa under Vespasian and Titus; he served, too, against the Parthians, and won the highest military distinction open to a subject, the grant of the triumphal insignia. Thus he acquired a prominent place among the brand new patricians created by the Flavians as substitutes for the nobles of old descent who had succumbed to the cruelty and rapacity of the emperors from Tiberius to Nero.
The younger Trajan was rigorously trained by his father, and deeply imbued with the same principles and tastes. He was a soldier born and bred. No better representative of the true old hardy Roman type, little softened either by luxury or education, had come to the head of affairs since the days of Marius. The date of his birth was probably 53 A.D. His training was almost exclusively military, but his experience as an officer gave him an acquaintance with almost every important province of the empire, which was of priceless value to him when he came to the throne. For ten years he held a commission as military tribune, which took him to many lands far asunder; then he filled important posts in Syria and Spain. How much actual warfare Trajan saw in those days we can hardly tell; he certainly went through some severe service under his father's command against the Parthians. By the year 89 he had achieved a considerable reputation. At that time L. Antonius Saturninus headed a rebellion in Germany, which threatened seriously to bring Domitian's rule to an end. Trajan was ordered in hot haste from Farther Spain to the Rhine. Although he carried his troops over that long and arduous march with almost unexampled rapidity, he only arrived after the insurrection had been put down. But his promptitude raised him higher in the favor of Domitian, and he was advanced to the consulship in 91. Of the next five years of his life we know nothing positively. It is not unlikely that they were spent at Rome or in Italy in the fulfilment of some official duties.
When the revolution of 96 came, and Nerva replaced the murdered Domitian, Trajan had conferred upon him one of the most important posts in the Empire, that of consular legate of Upper Germany. An officer whose nature, as the event showed, was interpenetrated with the spirit of legality, was a fitting servant of a revolution whose aim it was to substitute legality for personal caprice, as the dominant principle of affairs. The short reign of Nerva really did start the Empire on a new career, which lasted more than three-quarters of a century. But it also demonstrated how impossible it was for any one to govern at all who had no claim, either personal or inherited, to the respect of the legions. Nerva saw that if he could not find an Augustus to control the army, the army would find another Domitian to trample the Senate under foot. In his difficulties he took counsel with L. Licinius Sura, a lifelong friend of Trajan, and in October, 97, he ascended the Capitol, and with all due solemnity proclaimed that he adopted Trajan as his son.
The Senate confirmed the choice, and acknowledged the emperor's adopted son as his successor. In a letter which Nerva sent at once to Trajan, he quoted most significantly a line from the beginning of the "Iliad," where Chryses, insulted by Achilles, prays to Apollo: "May thy shafts afford me vengeance on the Greeks for my tears." After a little hesitation Trajan accepted the position, which was marked by the titles of Imperator, Cæsar, and Germanicus, and by the tribunician authority. He immediately proceeded to Lower Germany, to assure himself of the fidelity of the troops in that province, and while at Cologne he received news of Nerva's death (January, 98).
The authority of the new emperor was recognized at once all the Empire over. The novel fact that a master of the Romans should have been born on Spanish soil seems to have passed with little remark, and this very absence of notice is significant. Trajan's first care as emperor was to write to the Senate an assurance like that which had been given by Nerva, that he would neither kill nor degrade any senator. He ordered the establishment of a temple and cult in honor of his adoptive father, but he did not present himself at Rome for nearly two years after his accession. Possibly he had taken measures before Nerva's death to secure the revenge which Nerva craved, but probably did not live to see. In his dealings with the mutinous prætorians the strength of the new emperor's hand was shown at once. He ordered a portion of the force to Germany. They did not venture to disobey, and were distributed among the legions there. Those who remained at Rome were easily overawed and reformed. It is still more surprising that the soldiers should have quietly submitted to a reduction in the amount of the donative or gift which it was customary for them to receive from a new emperor, though the civil population of the capital were paid their largess (congiarium) in full. By politic management Trajan was able to represent the diminution as a sort of discount for immediate payment, while the civilians had to wait a considerable time before their full due was handed to them.
The secret of Trajan's power lay in his close personal relations with the officers and men of the army, and in the soldierly qualities which commanded their esteem. He possessed courage, justice, and frankness to a high degree. Having a good title to military distinction himself, he could afford, as the unwarlike emperors could not, to be generous to his officers. The common soldiers, on the other hand, were fascinated by his personal prowess and his somewhat ostentatious camaraderie. His features were firm and clearly cut; his figure was tall and soldierly, and exhibited the sinewy hard health of a veteran campaigner. His hair was already gray before he came to the throne, though he was not more than forty-four years old. The stoutness of the emperor's arm had been proved in the face of his men in many a hard fight. When on service he used the mean fare of the common private, dining on salt pork, cheese, and sour wine. Nothing pleased him better than to take part with the centurion, or the soldier in fencing or other military exercise, and he would applaud any shrewd blow which fell upon his own helmet. He loved to display his acquaintance with the career of distinguished veterans, and to talk with them of their battles and their wounds. Probably he lost nothing of his popularity with the army by occasional free indulgence in sensual pleasures, with which, as Bacon remarks, the soldier is apt to pay himself for the perils he encounters. Yet every man felt and knew that no detail of military duty, however minute, escaped the emperor's eye, and that any relaxation of discipline would be rigidly punished, yet with unwavering justice.
Trajan emphasized at once his personal control and the constitutionality of his sway, by bearing on his campaigns the actual title of "proconsul," which no other emperor had done. All things considered, it is not surprising that he was able, without serious opposition from the army, to remodel the whole military institutions of the empire, and to bring them into a shape from which there was comparatively little departure so long as the army lasted. In disciplinary matters no emperor since Augustus had been able to keep so strong a control over the troops. Pliny rightly praises Trajan as the lawgiver and the founder of discipline, and Vegetius classes Augustus, Trajan, and Hadrian together as restorers of the morale of the army. The confidence which existed between Trajan and his army finds expression in some of the coins of his reign.
For nearly two years after his election Trajan did not appear in Rome. He had decided already what the great task of his reign should be—the establishment of security upon the dangerous north-eastern frontier. Before visiting the capital he determined to put affairs in train for the attainment of this great object. He made a thorough inspection of the great lines of defence between the Danube and the Rhine, and framed, and partly carried out, a vast scheme for strengthening and securing them. The policy of opposing uncivilized tribes by the construction of the limes, a raised embankment of earth or other material, intersected here and there by fortifications, was not his invention, but it owed in great measure its development to him. This grand work, which would have excited the envy of Augustus, is traceable in its main extent at the present day. Among a people of roadmakers, Trajan was one of the greatest, and we have definite evidence from inscriptions that some of the military roads in this region were constructed by him. The more secure control which the Romans now maintained over the territory within the limes, tended to its rapid civilization, and the Roman influence, if not the Roman arms, soon began to affect powerfully the regions beyond.
After his careful survey of the Rhine end of the great defensive barrier, Trajan proceeded to consider it and plan it from the Danube. From the age of Tiberius onward, the Romans possessed the whole southern bank of the river from its source to the Euxine. But the precarious tenure of their possession, had been deeply impressed on them by the disasters and humiliations they had undergone in these districts during the reign of Domitian. A prince had arisen among the Dacians, Decebalus by name, worthy to be placed at the head of all the great barbarian antagonists of Rome. Like Maroboduus, he was able to combine the forces of tribes commonly hostile to each other, and his military ability almost went the length of genius. After he had swept the province of Mœsia bare, he was defeated by one of Domitian's lieutenants, but the position of affairs on the Danubio-Rhenish border was still so threatening, that the emperor was glad to conclude a treaty which conferred extraordinary advantages on his foe. Not only did the Romans stipulate to pay to Decebalus an annual subsidy, which he must have regarded as a tribute, but they agreed to supply him with engineers and craftsmen skilled in all kinds of construction, but particularly in the erection of fortifications and defensive works. During the nine or ten years which had elapsed since the conclusion of this remarkable treaty, the Dacian prince had immensely strengthened the approaches to his kingdom from the Roman side. He had also equipped and drilled his formidable army after the Roman fashion. It was impossible for a soldier like Trajan to endure the conditions laid down by Domitian; but the conquest of Dacia had become one of the most formidable tasks that had ever confronted the Empire. Trajan, no doubt, planned a war before he left the Danube for Rome late in 99.