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 A.D. 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 re-storers 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 dearly 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 northeastern 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.

The arrival of the emperor had been awaited in the capital with an impatience which is expressed by Pliny and by Martial. All that had happened since Trajan's elevation to the throne had raised high at Rome the hope of a prosperous and glorious reign. As he entered the city and went on foot to the Capitol, the plaudits of the people were unmistakably genuine. During his stay in the city he riveted more firmly still the affections both of the Senate and of the people. The reconciliation of the Empire with liberty, inaugurated, as Tacitus says, by Nerva, seemed now to be securely achieved. Trajan was absolutely open and simple, and lived with men at Rome as he had lived with his soldiers while on service. He realized the Senate's ideal of the citizen ruler. The assurance that no senator should suffer was renewed by oath. All the old republican formalities were most punctiliously observed—even those attendant on the emperor's election to the consulate, so far as they did not involve a restoration of the old order of voting at the comitia. The veneration for republican tradition is curiously attested by the reproduction of many republican types of coin struck by senatorial officers.

Trajan seized every opportunity for emphasizing his view that the princes  was merely the greatest of the magistrates, and so was not above but under the laws. He was determined, he said, to be to his subjects such a ruler as he had desired for himself when a subject. There is a pretty story to the effect that he handed the commander of the prætorians his sword, and said, "Use it for me if I do well, but against me if I do ill." Martial, who had called Domitian his lord and his god, now cried, "In him we have no lord, but an imperator!" Real power and influence were accorded to the Senate, which had now, by the incorporation of members whose origin was provincial, become in a manner representative of the whole empire. Trajan associated with the senators on equal terms, and enjoyed in their company every kind of recreation. All pomp was distasteful to him, and discarded by him. There was practically no court, and no intrigues of any kind were possible. The approach to his house was free, and he loved to pass through the city unattended, and to pay unexpected visits to his friends. He thirsted for no senator's blood, and used severity against the delatores  alone. There was but one insignificant conspiracy against him during his whole reign.

Though not literary himself, Trajan conciliated the literary men, who at all times had close relations with the Senate. His intimate, M. Licinius, played to excellent Mæcenas to his Augustus. In his efforts to win the affections of Roman society, Trajan was excellently aided by his wife Plotina, who was as simple as her husband, benevolent, pure in character, and entirely unambitious. The hold which Trajan acquired over the people was no less firm than that which he maintained upon the army and the Senate. His largesses, his distributions of food, his public works, and his spectacles were all on a generous scale. The exhibitions in the arena were perhaps at their zenith during his tenure of power. Though, for some unexplained reason, he abolished the mimes, so beloved of the populace, at the outset of his reign, he availed himself of the occasion of his first triumph to restore them again. The people were delighted by the removal of the imperial exedra  in the circus, whereby five thousand additional places were provided. Taxation was in many directions reduced, and the financial exactions of the imperial officers controlled by the erection of a special court. Elaborate precautions were taken to save Italy from famine; it is said that corn for seven years' consumption at the capital was retained in the granaries. Special encouragement was given to merchants to import articles of food. The corporation of bakers was organized, and made more effective for the service of the public. The internal trade of Italy was powerfully stimulated by the careful maintenance and extension of the different lines of road.

But the most striking evidence of Trajan's solicitude for his people's welfare is found in his institution of the alimenla, whereby means were provided for the rearing of poor and orphan children in Italy. The method had been sketched out by Nerva, but its great development was due to Trajan. The moneys allotted by the emperor were in many cases supplemented by private benevolence. As a soldier, Trajan realized the need of men for the maintenance of the Empire against the outer barbarians, and he preferred that these men should be of Italian birth. He was only carrying a step further the policy of Augustus, who by a system of rewards and penalties had tried to encourage marriage and the nurture of children. The annual effect of Trajan's regulations is hard to measure; they were probaby more effectual for their object than those of Augustus. The foundations were confiscated by Pertinax, after they had existed less than a century.

Toward the end of 100, or early in 101, Trajan left Rome for the Danube. Pretexts for a Dacian war were not difficult to find. Although there was no lack of hard fighting, victory in this war depended largely on the work of the engineer. The great military road connecting the posts in Upper Germany with those on the Danube, which had been begun by Tiberius, was now extended along the right bank of the river as far as the modern Orsova. The year 101 was spent mainly in roadmaking and fortification. In the following campaign, after desperate fighting to the north of the Danube in the mountainous region of Transylvania, such as Cæsar never encountered in all his Gaulish wars, the capital of Decebalus was taken, and he was forced to terms. He agreed to raze all forttesses, to surrender all weapons, prisoners, and Roman deserters, and to become a dependent prince under the suzerainty of Rome. Trajan came back to Italy with Dacian envoys, who in ancient style begged the Senate to confirm the conditions granted by the commander in the field. The emperor now enjoyed his first Dacian triumph, and assumed the title of Dacicus. At the same time he royally entertained the people, and no less royally rewarded his brave officers.

But the Dacian chief could not school his high spirit to endure the conditions of the treaty, and Trajan soon found it necessary to prepare for another war. A massive stone bridge was built across the Danube, near the modern Turn Severin, by Apollodorus, the gifted architect who afterward designed the forum of Trajan. In 105 began the new struggle, which on the side of Decebalus could now only lead to victory or to destruction. The Dacians fought their ground inch by inch, and their army as a whole may be said to have bled to death. The prince put an end to his own life. His kingdom became an imperial province; in it many colonies were founded, and peopled by settlers drawn from different parts of the empire. The work done by Trajan in the Danubian regions left a lasting mark upon their history. The emperor returned to the capital in 106, laden with captured treasure. His triumph outdid in splendor all those that went before it. Games are said to have been held continuously for four months. The chariot races were the grandest ever seen. Ten thousand gladiators contended in the arena, and eleven thousand beasts were killed in the contests. Congratulatory embassies came from all lands, even from India. The grand and enduring monument of the Dacian wars is the noble pillar which still stands on the site of Trajan's forum at Rome. The end of the Dacian wars was followed by seven years of peace.

Many details in the administration of the law, and particularly of the criminal law, were improved. To cure corruption in the Senate the ballot was introduced at elections to magistracies. The finances of the state were economically managed, and taxpayers were most carefully guarded from oppression. Trajan never lacked money to expend on great works of public utility; as a builder, he may fairly be compared with Augustus. His forum and its numerous appendages were constructed on a magnificent scale. Many regions of Italy and the provinces, besides the city itself, benefited by the care and munificence which the emperor bestowed on such public improvements. His attitude toward religion was, like that of Augustus, moderate and conservative. The famous letter to Pliny about the Christians is, according to Roman ideas, merciful and considerate. It was impossible, however, for a Roman magistrate of the time to rid himself of the idea that all forms of religion must do homage to the civil power. Hence the conflict which made Trajan appear in the eyes of Christians like Tertullian, the most infamous of monsters. On the whole, Trajan's civil administration was sound, careful, and sensible, rather than brilliant or epoch-making.

In 113 or 114 Trajan left Italy to make war in the East. The never-ending Parthian problem confronted him, and with it were more or less connected a number of minor difficulties. Already by 106 the position of Rome in the East had been materially improved by the peaceful annexation of districts bordering on the province of Syria. The district of Damascus, hitherto a dependency, and the last remaining fragment of the Jewish kingdom, were incorporated with Syria; Bostra and Petra were permanently occupied, and a great portion of the Nabathæan kingdom was constituted the Roman province of Arabia. Rome thus obtained mastery of the most important positions lying on the great trade-routes from East to West. These changes could not but affect the relations of the Roman with the Parthian empire, and the affairs of Armenia became, in 114, the occasion of war. Trajan's campaigns in the East ended in complete though brilliant failure. In the retreat from Ctesiphon (117), the old emperor tasted for almost the first time the bitterness of defeat in the field. He attacked the desert city of Hatra, westward of the Tigris, whose importance is still attested by grand ruins. The want of water made it impossible to maintain a large force near the city, and the brave Arabs routed the Roman cavalry. Trajan, who narrowly escaped being killed, was forced to withdraw.

A more alarming difficulty lay before him. Taking advantage of the absence of the emperor in the far East, and possibly by an understanding with the leaders of the rising in Armenia and the annexed portions of Parthia, the Jews all over the East had taken up arms at the same moment, and at a given signal. The massacres they committed were portentous. In Cyprus 240,000 men are said to have been put to death, and at Cyrene 220,000. At Alexandria, on the other hand, many Jews were killed. The Romans punished massacre by massacre, and the complete suppression of the insurrection was long delayed, but the Jews made no great stand against disciplined troops. Trajan still thought of returning to Mesopotamia, and of avenging his defeat at Hatra, but he was stricken with sickness and compelled to take ship for Italy. His illness increasing, he landed in Cilicia, and died at Selinus in that country about the end of July, 117.

Trajan, who had no children, had continually delayed to settle the succession to the throne, though Pliny, in the "Panegyric" had pointedly drawn his attention to the matter, and it must have caused the Senate much anxiety. Whether Hadrian, the cousin of Trajan, was actually adopted by him or not, is impossible to determine; certainly Hadrian had not been advanced to any great honors by Trajan. Even his military service had not been distinguished. Plotina asserted the adoption, and it was readily and most fortunately accepted, if not believed, as a fact.

The Senate had decreed to Trajan as many triumphs as he chose to celebrate. For the first time a dead general triumphed. When Trajan was deified, he appropriately retained, alone among the emperors, a title he had won for himself in the field, that of "Parthicus." He was a patient organizer of victory rather than a strategic genius. He laboriously perfected the military machine, which when once set in motion went on to victory. Much of the work he did was great and enduring, but the last year of his life forbade the Romans to attribute to him that felicitas  which they regarded as an inborn quality of the highest generals. Each succeeding emperor was saluted with the wish that he might be "better than Trajan and more fortunate than Augustus." Yet the breach made in Trajan's felicitas  by the failure in the East was no greater than that made in the felicitas  of Augustus by his retirement from the right bank of the Rhine.