On Dec. 22, 69, the Senate conferred all the imperial powers upon Vespasian en bloc with the famous Lex de Imperio Vespasiani (“Law Regulating Vespasian’s authority”), and the Assembly ratified the Senate’s action. This apparently was the first time that such a law was passed; a fragmentary copy of it is preserved on the Capitol in Rome.

Vespasian (ruled 69–79) did not originate from Rome or its aristocracy. His family came from the Sabine municipality Reate, and with his elevation the Italian bourgeoisie came into its own. He and his two sons, both of whom in turn succeeded him, constituted the Flavian dynasty (69–96). Vespasian faced the same difficult task as Augustus—the restoration of peace and stability. The disorders of 69 had taken troops away from the Rhine and Danube frontiers. Thereupon, the Danubian lands were raided by Sarmatians, a combination of tribes who had overwhelmed and replaced the Scythians, their distant kinsmen, in eastern Europe. The assailants were repelled without undue difficulty; but the Sarmatian Iazyges, now firmly in control of the region between the Tisza and Danube rivers, posed a threat for the future.

Developments in the Rhineland were more immediately serious. There in 69 a certain Civilis incited the Batavians serving as auxiliaries in the Roman army to rebel. Gallic tribes joined the movement, and the insurgents boldly overran all but two of the legionary camps along the Rhine. Vespasian sent his relative Petilius Cerealis to deal with the rebels, who, fortunately for Rome, were not united in their aims; by 70 Cerealis had restored order. That same year Vespasian’s elder son, Titus, brought the bloody war in Judaea to its end by besieging, capturing, and destroying Jerusalem.

To rehabilitate the public finances, Vespasian introduced new imposts, including a poll tax on Jews, and practiced stringent economies. With the Senate he was courteous but firm. He allowed it little initiative but used it as a reservoir from which to obtain capable administrators. To that end he assumed the censorship and added senators on a larger scale than Claudius had done, especially from the municipalities of Italy and the western provinces. Already before 69 an aristocracy of service had arisen, and the provincialization of the Roman Senate had begun; thereafter this development made rapid headway. Besides the censorship, Vespasian also often held the consulship, usually with Titus as his colleague. His object presumably was to ensure that his own parvenu Flavian house outranked any other. In this he succeeded; the troops especially were ready to accept the Flavians as the new imperial family. On Vespasian’s death in 79, Titus, long groomed for the succession, became emperor and immediately had his father deified.

Titus (ruled 79–81) had a brief reign, marred by disasters (the volcanic eruption that buried Pompeii and Herculaneum and another great fire in Rome); but his attempts to alleviate the suffering and his general openhandedness won him such popularity that he was unhesitatingly deified after his early death.

Domitian (ruled 81–96), Titus’ younger brother, had never been formally indicated for the succession; but the praetorians acclaimed him, and the Senate ratified their choice. Throughout his reign Domitian aimed at administrative efficiency, but his methods were high-handed. For him the Senate existed merely to supply imperial servants. He also used equites extensively, more than any previous emperor. He held the consulship repeatedly, was censor perpetuus from 85 on, and demanded other extravagant honours. On the whole, his efficiency promoted the welfare of the empire. Above all, he retained the allegiance of the troops. Although scornful of the Senate’s dignity, he insisted on his own and mercilessly punished any act of disrespect, real or fancied, toward himself. He became even more suspicious and ruthless when Saturninus, commander in Upper Germany, attempted rebellion in 89. He crushed Saturninus; executions and confiscations ensued, and delatores flourished. The tyranny was particularly dangerous to senators, and it ended only with Domitian’s assassination in 96. The Flavian dynasty, like the Julio-Claudian, ended with an emperor whose memory was officially damned.

The disorders in 69 were the cause of some military reforms. Under the Flavians, auxiliaries usually served far from their native hearths under officers of different nationality from themselves. At the same time, the tasks assigned to them came increasingly to resemble those performed by the legionaries. The latter grew less mobile, as camps with stone buildings came to be the rule; and it became common for detachments from a legion (vexillationes), rather than the entire legion, to be used for field operations. This army of a new type proved its mettle in Britain, where the advance halted by Boudicca’s revolt was now resumed. Between 71 and 84 three able governors—Petilius Cerealis, Julius Frontinus, and Julius Agricola, the latter Tacitus’ father-in-law—enlarged the province to include Wales and northern England; Agricola even reached the Scottish highlands before Domitian recalled him.

Along the Rhine, weaknesses revealed by Civilis’ revolt were repaired. Vespasian crossed the river in 74 and annexed the Agri Decumates, the triangle of land between the Rhine, Danube, and Main rivers. To consolidate the position, he and Domitian after him penetrated the Neckar River valley and Taunus mountains, and fortifications began to take shape to the east of the Rhine, a military boundary complete with strongpoints, watchtowers, and, later, a continuous rampart of earthworks and palisades. Once Saturninus’ revolt in 89 had been suppressed, Domitian felt the situation along the Rhine sufficiently stable to warrant conversion of the military districts of Upper and Lower Germany into regular provinces and the transfer of some Rhineland troops to the Danube. To the north of this latter river, the Dacians had been organized into a strong kingdom, ruled by Decebalus and centring on modern Romania; in 85 they raided southward across the Danube, and in the next year they defeated the Roman punitive expedition. Domitian restored the situation in 88, but Saturninus’ rebellion prevented him from following up his success. Domitian and Decebalus thereupon came to terms: Decebalus was to protect the lower Danube against Sarmatian attack, and Domitian was to pay him an annual subsidy in recompense. The Danubian frontier, however, remained disturbed, and Domitian wisely strengthened its garrisons; by the end of his reign it contained nine legions, as against the Rhineland’s six, and Pannonia was soon to become the military centre of gravity of the empire.

The Flavians also took measures to strengthen the eastern frontier. In Asia Minor, Vespasian created a large “armed” province by amalgamating Cappadocia, Lesser Armenia, and Galatia; and the whole area was provided with a network of military roads. South of Asia Minor, Judaea was converted into an “armed” province by getting legionary troops; and two client kingdoms—Commagene and Transjordan—were annexed and added to Syria. Furthermore, the legionary camps seem now to have been established right on the Euphrates at the principal river crossings. This display of military strength kept the empire and Parthia at peace for many years.

The early Antonine emperors: Nerva and Trajan

Marcus Cocceius Nerva, an elderly senator of some distinction, was the choice of Domitian’s assassins for emperor; and the Senate promptly recognized him. The soldiers, however, did so much more reluctantly, and, because the year 69 had revealed that emperors no longer needed to be Roman aristocrats and could be chosen in places other than Rome, their attitude imposed caution.

Nerva, who ruled from 96 to 98, adopted a generally lavish and liberal policy, but it failed to win the soldiers over completely, and he proved unable to save all Domitian’s murderers from their vengeance. Unrest subsided only when, overlooking kinsmen of his own, he adopted an outstanding soldier, Marcus Ulpius Trajanus, who was governor of Upper Germany, as his successor. Nerva himself died a few months later.

Trajan (ruled 98–117) was the first and perhaps the only emperor to be adopted by a predecessor totally unrelated to him by either birth or marriage. He was also the first in a series of “good” rulers who succeeded one another by adoption and for most of the 2nd century provided the empire with internal harmony and careful government; they are collectively, if somewhat loosely, called the Antonine emperors. More significantly still, Trajan, a Spaniard, was also the first princeps to come from the provinces; with the greater number of provincials now in the Senate, the elevation of one of them, sooner or later, was practically inevitable. Throughout his reign, Trajan generally observed constitutional practices. Mindful of the susceptibilities of the Senate, he regularly consulted and reported to it. Modest in his bearing, he did not claim ostentatious honours such as frequent consulships or numerous imperial salutations, and he mixed easily with senators on terms of cordial friendship. This reestablished mutual respect between princeps and Senate. Empire and liberty, in Tacitus’ words, were reconciled, and the atmosphere of suspicion, intrigue, and terror surrounding the court in Domitian’s day disappeared. Trajan endeared himself also to the populace at large with lavish building programs, gladiatorial games, and public distributions of money. Above all, he was popular with the armed forces; he was the soldier-emperor par excellence. Understandably, he received the title Optimus (Best), officially from 114 on (and unofficially for many years earlier).

Yet Trajan was a thoroughgoing autocrat who intervened without hesitation or scruple even in the senatorial sphere, whenever it seemed necessary. His aim was efficiency; his desire was to promote public welfare everywhere. He embellished Rome with splendid and substantial structures, and he showed his care for Italy by refurbishing and enlarging the harbours at Ostia, Centumcellae, and Ancona. He sent officials called curatores to Italian municipalities in financial difficulties and helped to rehabilitate them. He greatly expanded an ingenious charity scheme probably begun by Nerva: money was loaned to farmers on easy terms, and the low interest they paid went into a special fund for supporting indigent children. Nor did Trajan neglect Italy’s highway network: he built a new road (Via Traiana) that soon replaced the Via Appia as the main thoroughfare between Beneventum and Brundisium.

Interest in Italy implied no neglect of the provinces. Curatores were also sent to them; to rescue Achaea and Bithynia, senatorial provinces, from threatened bankruptcy, Trajan made them both temporarily imperial, sending special commissioners of his own to them. His correspondence with his appointee in Bithynia, the younger Pliny, has survived and reveals how conscientiously the emperor responded on even the smallest details. At the same time, it reveals how limited was access to the central government and, consequently, how great a latitude for independent decisions must be left to the governors who lacked some special claim on the emperor’s attention. Trajan’s day was too short to hear every speech of every delegation from the provinces, every recommendation to bestow favour or grant promotion, and every appeal to himself as supreme judiciary. To assist him, he had a “bureaucracy” of only a few hundred in Rome and a few more hundred serving in various capacities in the provinces—to direct the lives of some 60 million people. Clearly, most government must in fact rest in the hands of local aristocracies.

In the military sphere, Trajan’s reign proved a most dynamic one. He decided to strengthen the dangerous Danube frontier by converting Dacia into a salient of Roman territory north of the river in order to dismember the Sarmatian tribes and remove the risk of large, hostile combinations to a safer distance. Bringing to bear a force of 100,000 men, he conquered Decebalus in two hard-fought wars (101–102; 105–106) and annexed Dacia, settling it with people from neighbouring parts of the empire. On the eastern frontier he planned a similar operation, evidently in the conviction, shared by many eminent Romans both before and after him, that only conquest could solve the Parthian problem. Possibly, too, he wished to contain the menace of the Sarmatian Alani in the Caspian region. In a preliminary move, the Nabataean kingdom of Arabia Petraea was annexed in 105–106. Then, in 114, Trajan assembled another large army, incorporated the client kingdom of Armenia, and invaded Parthia.

After spectacular victories in 115 and 116, he created additional provinces (Northern Mesopotamia, Assyria) and reached the Persian Gulf. But he had merely overrun Mesopotamia; he had not consolidated it, and, as his army passed, revolts broke out in its rear. The Jews of the Diaspora and others seized their chance to rebel, and before the end of 116 much of the Middle East besides Parthia was in arms (Cyrene, Egypt, Cyprus, Anatolia). Trajan proceeded resolutely to restore the situation, but death found him still in the East.

Before his last illness he had not formally indicated his successor. But high honours and important posts had been accorded his nearest male relative, Publius Aelius Hadrianus, the governor of Syria; and, according to Trajan’s widow, Hadrian had actually been adopted by Trajan on his deathbed. Accordingly, both Senate and soldiers recognized him. Trajan’s posthumous deification was never in doubt.

Hadrian and the other Antonine emperors

Hadrian (ruled 117–138), also a Spaniard, was an emperor of unusual versatility. Unlike Trajan, he was opposed to territorial expansion. Being himself in the East in 117, he renounced Trajan’s conquests there immediately and contemplated evacuating Dacia as well. Furthermore, four of the consular generals particularly identified with Trajan’s military ventures were arrested and executed “for conspiracy”; Hadrian claimed later that the Senate ordered their deaths against his wishes. The only heavy fighting during his generally peaceful reign occurred in Judaea—or Syria Palaestina, as it was thenceforth called—where Bar Kokhba led a furious, if futile, Jewish revolt (132–135) against Hadrian’s conversion of Jerusalem into a Roman colony named Aelia Capitolina.

Instead of expansion by war, Hadrian sought carefully delimited but well-defended frontiers, with client states beyond them where possible. The frontiers themselves, when not natural barriers, were strongly fortified: in Britain, Hadrian’s Wall, a complex of ditches, mounds, forts, and stone wall, stretched across the island from the Tyne to the Solway; Germany and Raetia had a limes (fortified boundary) running between Mainz on the Rhine and Regensburg on the Danube. Within the frontiers the army was kept at full strength, mostly by local recruiting of legionaries and apparently of auxiliaries, too (so that Vespasian’s system of having the latter serve far from their homelands gradually ceased). Moreover, the tendency for auxiliaries to be assimilated to legionaries continued; even the officers became less distinguishable, because equites now sometimes replaced senators in high posts in the legions. To keep his essentially sedentary army in constant readiness and at peak efficiency (no easy task), Hadrian carried out frequent personal inspections, spending about half his reign in the provinces (121–125; 128–134).

Hadrian also was responsible for significant developments on the civilian side. Under him, equites were no longer required to do military service as an essential step in their career, and many of them were employed in the imperial civil service, more even than under Domitian. By now the formative days of the civil service were over; its bureaucratic phase was beginning, and it offered those equites who had no military aspirations an attractive, purely civilian career. Formal titles now marked the different equestrian grades of dignity: a procurator was vir egregius; an ordinary prefect, vir perfectissimus; a praetorian prefect, vir eminentissimus, the latter title being obviously parallel to the designation vir clarissimus for a senator. Thenceforth, equites replaced freedmen in the imperial household and bureaus, and they even appeared in Hadrian’s imperial council.

Hadrian also improved legal administration. He had his expert jurists codify the edictum perpetuum (the set of rules gradually elaborated by the praetors for the interpretation of the law). He also appointed four former consuls to serve as circuit judges in Italy. This brought Italy close to becoming a province; Hadrian’s intent, however, was not to reduce the status of Italy but to make all parts of the empire important. For one part of his realm, he was exceptionally solicitous: he spent much time in Greece and lavishly embellished Athens.

Hadrian maintained good relations with but was never fully trusted by the Senate. His foreign policy seemed to be unheroic, his cosmopolitanism to be un-Roman, and his reforms to encroach on activities traditionally reserved for senators. Moreover, in his last two years he was sometimes capricious and tyrannous. Like Augustus, he had no son of his own and conducted a frustrating search for a successor. After executing his only male blood relative, his grandnephew, in 136, he adopted Lucius Ceionius Commodus, renaming him Lucius Aelius Caesar. The latter, however, died shortly afterward, whereupon Hadrian in 138 chose a wealthy but sonless senator, the 51-year-old Titus Aurelius Antoninus; but, evidently intent on founding a dynasty, he made Antoninus in his turn adopt two youths, 16 and 7 years old, respectively—they are known to history as Marcus Aurelius (the nephew of Antoninus’ wife) and Lucius Verus (the son of Aelius Caesar). When Hadrian died soon thereafter, Antoninus succeeded and induced a reluctant Senate to deify the deceased emperor. According to some, it was this act of filial piety that won for Antoninus his cognomen, Pius.

Antoninus Pius (ruled 138–161) epitomizes the Roman Empire at its cosmopolitan best. He himself was of Gallic origin; his wife was of Spanish origin. For most men his was a reign of quiet prosperity, and the empire under him deserves the praises lavished upon it by the contemporary writer Aelius Aristides. Unlike Hadrian, Antoninus traveled little; he remained in Italy, where in 148 he celebrated the 900th anniversary of Rome. Princeps and Senate were on excellent terms, and coins with the words tranquillitas and concordia on them in Antoninus’ case mean what they say. Other of his coins not unreasonably proclaim felicitas temporum (“the happiness of the times”). Yet raids and rebellions in many of the borderlands (in Britain, Dacia, Mauretania, Egypt, Palaestina, and elsewhere) were danger symptoms, even though to the empire at large they seemed only faraway bad dreams, to use the expression of Aelius Aristides. Antoninus prudently pushed the Hadrianic frontiers forward in Dacia, the Rhineland, and Britain (where the Antonine Wall from the Firth of Forth to the River Clyde became the new boundary) and carefully groomed his heir apparent for his imperial responsibilities.

Marcus Aurelius (ruled 161–180) succeeded the deified Antoninus and more than honoured Hadrian’s intentions by immediately co-opting Lucius Verus as his full co-emperor. Because Verus’ competence was unproved, this excess of zeal was imprudent. Fortunately, Verus left decision making to Marcus. Marcus’ action was also dangerous for another reason; it represented a long step away from imperial unity and portended the ultimate division of the empire into Greek- and Latin-speaking halves. Nor was this the only foreboding development in Marcus’ reign—formidable barbarian assaults were launched against the frontiers, anticipating those that were later to bring about the disintegration of the empire. Marcus himself was a stoic philosopher; his humanistic, if somewhat pessimistic, Meditations reveal how conscientiously he took his duties. Duty called him to war; he responded to the call and spent far more of his reign in the field than had any previous emperor.

At Marcus’ very accession the Parthians turned aggressive, and he sent Verus to defend Roman interests (162). Verus greedily took credit for any victories but left serious fighting to Avidius Cassius and the army of Syria. Cassius succeeded in overrunning Mesopotamia and even took Ctesiphon, the Parthian capital; he was therefore able to conclude a peace that safeguarded Rome’s eastern provinces and client kingdoms (166). In the process, however, his troops became infected with plague, and they carried it back with them to the west with calamitous results. The Danube frontier, already weakened by the dispatch of large detachments to the East, collapsed under barbarian assault. Pressed on from behind by Goths, Vandals, Lombards, and others, the Germanic Marcomanni and Quadi and the Sarmatian Iazyges poured over the river; the Germans actually crossed Raetia, Noricum, and Pannonia to raid northern Italy and besiege Aquileia. Marcus and Verus relieved the city shortly before Verus’ death (169). Then, making Pannonia his pivot of maneuver, Marcus pushed the invaders back; by 175 they were again beyond the Danube. At that moment, however, a false report of Marcus’ death prompted Avidius Cassius, by now in charge of all eastern provinces, to proclaim himself emperor. The news of this challenge undid Marcus’ achievements along the Danube because it took him to the East and reopened the door to barbarian attacks. Fortunately, Cassius was soon murdered, and Marcus could return to central Europe (177). But he had barely restored the frontier again when he died at Vindobona (Vienna) in 180, bequeathing the empire to his son, the 19-year-old Commodus, who had actually been named coemperor three years earlier.

Commodus (ruled 180–192), like Gaius and Nero, the youthful emperors before him, proved incompetent, conceited, and capricious. Fortunately, the frontiers remained intact, thanks to able provincial governors and to barbarian allies, who had been settled along the Danube with land grants and who gave military service in return. But Commodus abandoned Marcus’ scheme for new trans-Danubian provinces, preferring to devote himself to sensual pleasures and especially to the excitements of the arena in Rome, where he posed as Hercules Romanus and forced the Senate to recognize his godhead officially. He left serious business to his favourites, whose ambitions and intrigues led to plots, treason trials, confiscations, and insensate murders. Commodus’ assassination on the last day of 192 terminated a disastrous reign; thus the Antonines, like the Julio-Claudians, had come to an ignominious end. And there was a similar sequel. Commodus’ damnatio memoriae, like Nero’s, was followed by a year of four emperors.