The Roman Empire began under the first emperor, Augustus, in the 1st century BCE. This article covers the history of the Roman Empire up to the early 3rd century CE.
The earlier history of Rome – its expansion from city-state to world power – is dealt with in the article, the Rise of the Roman Empire, while the article, The Late Roman Empire, deals with the later stages of Rome’s history.
For more on Roman society and culture, go to the article on the Civilization of Ancient Rome.
The Roman Empire was established on the wreckage of the Roman Republic, and came about as a result of Augustus’ overwhelming dominance of the Roman state.
This dominance rested on a package of political measures known (by modern scholars) as the Augustan settlement. By this, the outward form of the Republic was maintained, but he gained direct and indirect control over appointments to all the high offices of the Roman state – army commands, provincial administrators, and senior government posts in Rome itself. He also acquired affective control over all policy matters.
This Augustan settlement inaugurated the Roman Empire. It formed the basis on which Augustus’ successors exercised overwhelming power within the state, thereby providing it with a monarchical framework of government. This gave the Roman world an internal peace and stability which mostly held for more than two hundred years.
[Click here for more on the position of the emperor in the first two centuries of the Roman Empire]
Imperial Expansion under Augustus
Augustus was sole master of the Roman world for more than forty years (31 BCE to 14 CE). Along the eastern frontier he brought Armenia into the Roman sphere and stabilized the frontier with Parthia; by forceful diplomacy he was also able to have the legionary standards lost at the disaster of Carrhae returned to the Romans.
In a vast series of conquests his generals annexed the wild lands of the Balkans, pushing the Roman frontiers to the Danube, and moved the frontier with the Germans to the Elbe. These conquests were interrupted by a fierce rebellion in Danube lands that needed over half the imperial army to crush it. Then, in 9 CE, the Rhine army of three legions under Quintilius Varus was trapped deep in the Teutoburg forest in Germany, and wiped out. Augustus was deeply affected by this disaster, and made no further attempts at conquest. He left advice in his will that the borders of the Roman Empire should be left as they were.
The Julio-Claudian emperors after Augustus
Scholars often call the political system of the early empire the Principate, after one of the emperor’s main titles, princeps (somewhat loosely translated as “first citizen”). Such was the overwhelming bundle of powers that Augustus enjoyed that no one could stand against his wishes to transmit his position to a successor. A return to the Republican system would in any case have been completely impracticable.
The only question was, then, who should succeed Augustus?
During the first century of the empire, the emperors were members of what has been called the “Julio-Claudian” dynasty. This is something of a misnomer, as none of the emperors of this “dynasty” were able to transmit their power to a genetic offspring; however, they did all belong to an interrelated group of Patrician families clustered around the Julian or Claudian clans, either through birth, adoption or marriage, and were thus able to maintain a fiction of inherited power.
Since Augustus had no sons, and his nephew and grandsons had all died before him, he chose his step-son, Tiberius (a member of the Claudian clan) to follow him.
Tiberius (reigned 14-37 CE), though undoubtedly able, was elderly and gloomy, and probably alcoholic. For much of his reign his ruthless Praetorian Prefect, Sejanus, virtually ruled the empire until his downfall, which occurred when rumours surfaced that he was cooking up a plot against his master. In his last years Tiberius more or less retired to the island of Capri, off the coast of southern Italy, from where rumours of a depraved lifestyle filtered back to Rome.
Tiberius, as with Augustus having no surviving son, was succeeded by his great grand-nephew, Gaius (a member of the Julian clan, reigned 37-41 CE). Gaius, nicknamed “Caligula” (“Little Boots” after the small army boots he wore as a child when his father was a general), soon became insane. He lashed out at anyone he disliked or felt threatened by, and his blood-soaked rule was brought to an end when he was murdered by some of his servants and members of the Praetorian Guard.
In the chaotic scenes in the palace following Caligula’s murder, an elderly uncle of his (and grand-nephew of Augustus) was found by the guards and promptly elevated to the emperorship. This was Claudius (reigned 41-54 CE; as his name indicates, he was a Claudian).
Claudius had physical infirmities which made him liable to ridicule, but he was probably one of the most intelligent of all Roman emperors. It was during his reign that the conquest of Britain was launched.
He was not very sensible in his final marriage. The ambitious Agrippina had him adopt her son, Nero, and then, when he was 16, poisoned Claudius (or so it was generally believed).
Nero (who, as the adopted son of Claudius, was also therefore a Claudian) was the last of the Julio-Claudians. His reign (54-68 CE) was marked by more atrocities than any of his predecessors. He poisoned Claudius’ young son, Britannicus, murdered his mother Agrippina (after more than one attempt), divorced and executed his wife, Claudius’ daughter, and abandoned himself to various vices.
During Nero’s reign a huge fire destroyed a large section of Rome. Nero seems to have helped fund the rehousing of many people who had lost their homes, but he also used much of the land cleared by the fire on which to build a magnificent new palace. This was called the “Golden House”, due to its unparalleled splendour. This led to rumours that Nero himself had started the fire to enable him to build this palace. He tried to deflect the blame onto members of the new Christian religion, which, despite it being barely thirty years since its founder Jesus of Nazareth had lived and died in Judaea, was already well established in Rome. He was the first emperor to instigate an official persecution of Christians.
Nero’s extravagance and eccentricities (he was fond of acting in public, an unorthodox of thing for a Roman aristocrat to do), did not endear him to the troops on the frontiers. He lost the loyalty of the Roman armies, and in the late 60s, a rebellion in Spain led quickly to his suicide.
The political situation under the Julio-Claudians
By the time of Augustus’ death the principate was the only political system which most people could remember. Perhaps because of this a rosy glow now hung over the memory of the old republic. Some senators, and not only those from old families with generations of consuls behind them, still hankered after the good old days when the senate had ruled supreme and there was no princeps to dwarf its members in authority and prestige.
Throughout the Julio-Claudian period, there were repeated conspiracies against the emperors, hatched by groups of senators and equestrians. This created an ongoing tension between emperor and senate which was never far below the surface. Some emperors, such as Gaius and Nero, succumbed to paranoia, prompting them to unleash a lethal campaign on the senators, with as many as one in ten falling victim to their suspicions. At such times an atmosphere of fear prevailed in the corridors of power. Even under a more moderate emperor like Claudius, who probably shared many of the Republican sympathies of some senators, several senators were executed on suspicion of treason.
Even in normal times senators were in a difficult position. Although the senate still retained important powers, and was required to deliberate on weighty matters, ambitious senators were now dependant upon the princeps for high office. it was natural that they should try to vote strictly according to the wishes of the emperor. This rather undermined the purpose of the senate, and in frustration Tiberius, for example, tried to conceal his own opinions on subjects which came before it, so that a proper debate could take place. This only made senators believe that he was trying to trap them into indiscretions.
The events following the murder of Caligula showed up the real powerlessness of the senate as a political institution. On news of the murder the senate immediately began discussing restoring the Republic. The Praetorian Guard, however, had acclaimed Gaius’ uncle Claudius as emperor and the senate had no choice but to acquiesce.
The emperors needed the senate, however. This body was the fount of legitimacy; all the emperors’ offices and titles had been voted to them by the senate, and it was this fact that made the emperors’ position legal in the eyes of the Roman people. Moreover most of the emperors’ generals, governors, ministers and high officials were senators; he relied on their loyalty and good service, and he was not often disappointed.The majority of senators gave distinguished service, and even under the worst of rulers the empire continued to run smoothly. Finally, all the emperors at this period themselves came from the oldest and most prominent of the senatorial nobility – the Julian and Claudian clans, and the other ancient families to which they were related. It was unthinkable that they should do away with their own class.
The environment in which the emperor lived also gave another group some political importance – the Roman mob.
The emperors were regularly to be seen in public. They presided over games in the amphitheatre and races in the Circus Maximus; they took a central role in the festivities and rites of the state religion; they attended meetings of the senate; and some of them even visited public baths, mingling with fellow citizens on terms approaching equality. It is difficult for us today to imagine, removed as we are from the environment in which the politics of the principate took place, what it must have been like for an emperor and his entourage to be greeted by a huge and unruly crowd, angry at some policy or other. What is clear is that emperors were indeed as careful as they could be to keep on the right side of the Roman mob. Caligula once joked, “would that the Roman people had but one throat”. This points to the fact that, whereas he could threaten senators and other individuals into obedience, the mob was beyond his control.
The provinces and frontiers under the Julio-Claudians
Despite the personal failings of the Julio-Claudian emperors, the empire as a whole continued to be well governed. Peace prevailed throughout the provinces. The system which Augustus had established, by which senior army officers and provincial governors were appointed and promoted on the emperor’s say-so (though from a very narrow group within society, mostly senators, some equestrians), ensured a generally high standard of administration. Senior officials were well paid, discouraging corrupt practices; and provincials – especially the elites of the towns and cities of the empires – could take their complaints to the emperor if a governor was notably corrupt or incompetent.
In the first century of the empire Roman citizenship began to spread widely amongst the subject peoples of the empire. The ruling classes (equestrians and senators) also began to fill up with provincial families. Men from Spain were admitted into the senate in Augustus’ time (though he did try to keep the senate a mostly Italian body), and Claudius was the first to promote Gauls from north of the Alps (i.e from amongst those who were descended from Rome’s ancestral enemies, the tribes of modern-day France) to the senate.
The frontiers of the empire continued to advance. Tiberius was not particularly interested in new conquests – the disaster of the Tuetoburg Forest was probably still too fresh in the minds of Rome’s leaders in his time. Claudius however began the conquest of Britain (43 CE), where he made a brief personal appearance. He also extended Roman territory to cover the whole of north Africa. Under Nero there were continuing wars in Britain, where the revolt of the Iceni tribe, under their fierce queen Boudica, came perilously close to driving the Romans out of the island. After Boudica’s defeat Roman expansion in Britain resumed.
A war with the Parthian empire also broke out in Nero’s reign, over control of the kingdom of Armenia. The successes of Nero’s general Corbulo soon brought Parthia to the negotiating table and Armenia back into Rome’s sphere of influence.
At this point, however, a revolt broke out amongst the Jews in Judaea. This remained undefeated at the time of Nero’s death (see below).
Reports of Nero’s eccentric behaviour (especially his public stage appearances) reached the troops on the frontier; they were not impressed. They heard of his extravagances as well, especially his magnificent but hugely expensive “Golden House”. To complete this he had to raise extra taxes in the provinces, and even so, the payment of troops fell into areas. Also, his ordering of the suicide of his most famous general, Corbulo, who was very popular amongst his troops, infuriated them. By the late 60s the army was in a mutinous mood. In 68 a rebellion broke out in Spain. Nero found that none of the frontier armies would supported him, and he committed suicide, apparently saying “What an artist the world is losing in me!”.
With Nero’s suicide the Julio-Claudian house was now extinct: who would be emperor? In 68 and 69 CE four emperors came and went as different frontier armies marched on Italy is support of their own candidates (in each case, one of their senior generals). First Galba, the governor in Spain, was recognised as emperor by his troops and marched into Italy; he was soon murdered at the instigation of his lieutenant, Otho. Otho was a former friend of Nero who had the support of the Praetorian Guard (and who had been alarmed by the disciplinarian approach of Galba). Otho’s forces were soon defeated by the Rhine armies, who had acclaimed one of their commanders, Vitellius, as emperor. By the end of 69 Vitellius, too, had been murdered, and Flavius Vespasian, at the head of the eastern armies, was triumphant.
Vespasian (reigned 69-79 CE) was an experienced and able soldier, He came from comparatively humble origins in Italy, the grandson of a centurion, a far cry from the old Patrician stock of the Julio-Claudians.
Vespasian set about restoring order. He put the imperial finances on a firm footing by heavy taxation, and appointed able governors to restore order and good government to the provinces. In Rome he demolished Nero’s Golden House, which had become a by-word for extravagant waste, and on the land thus made vacant he started building a huge new amphitheatre, the Coliseum. partly to relieve unemployment in Rome. When he died he had gained the respect of the senate and was immediately deified.
During Vespasian’s reign, a great Jewish rebellion (see below) was crushed, by a Roman army under the command of his son, Titus.
On his death, Vespasian was succeeded by Titus (the first actual son of an emperor to follow his father on the throne; reigned 79-81 CE). The new emperor was easy-going and popular. He won further popularity by his generosity in helping the homeless victims of the eruption of Vesuvius, which completely destroyed the towns of Pompeii and Herculaneum.
Titus died after only two years in power, of natural causes. He was succeeded by his younger brother, Domitian.
Domitian (81-96 CE) was an efficient administrator, but merciless and suspicious. His behaviour provoked fear amongst those around him, and conspiracies, real and imagined, were launched against him. A reign of terror developed, as in the worst days of the Julio-Claudians; as then informers reigned supreme and senators in particular had to be very careful what they said and who they talked to. Eventually he was murdered by some of the palace servants.
The circumstances of Domitian’s death were not unlike that of the emperor Gaius (see above): killed within his palace by members of his own domestic staff. What followed next was quite different, and had enduring consequences. The Praetorian Guard kept out of events and the senate found itself played the key role of choosing the next emperor.
They chose an elderly senator, Cocceius Nerva (reigned 96-8), who ruled briefly and competently, and put an immediate stop to the reign of terror; but he was a stopgap choice. He was childless (like so many Roman aristocrats of the period), and by far the most important thing he did was to chose a highly suitable successor.
He adopted as son a respected general named Ulpius Traianus (Trajan). This ensured that his death was not followed by instability and civil war, and that sound rule continued.
Nerva and his successors who reigned from 96 to 180 CE are known as the “Five Good Emperors”. Until the last one, Marcus Aurelius, they were all without sons to succeed them, and they all (except Marcus) took steps, well before they died, to ensure that there would be a suitable successor.
Trajan (reigned 96-117 CE) came from a Roman family long settled in Spain. He was an ambitious soldier, and fought two major wars of conquest, in the Balkans and in the East (see below); under him the Roman empire reached its greatest extent.
He was succeeded by his cousin, Aelius Hadrianus (Hadrian, reigned 117-37 CE). After Trajan’s expansionism he pulled back behind defensible frontiers, which he strengthened: his most famous defence project is “Hadrian’s Wall”, in northern England. He adopted his relative Aurelius Antoninus as his successor, known to history as Antonius Pius (reigned 137-61). His was the most peaceful of any emperor’s reign.
He was succeeded by his adopted son Marcus Aurelius (161-180), who spent his whole reign campaigning on the Danubian frontier.
The political situation
Except for under the paranoid emperor Domitian, this period was much freer of tensions between emperors and senators than had been the case under the Julio-Claudians.
The civil wars of the Year of the Four Emperors had perhaps underscored for all (except perhaps the most die-hard republicans) where the realities of power now lay. As the historian Tacitus said, the “secret was out – emperors could be made outside Rome”. It was now plain that the Roman armies were the real source of power in the empire; while an emperor retained their loyalty he was virtually unassailable. Ironically, this encouraged the senators to devote their energies, not to opposition, but to loyal service to the emperors and in upholding the political order which now prevailed. Particularly under the Five Good Emperors, the political situation was marked by stability and quiet. The only dangerous moment was when rumours spread in the east that the emperor Marcus Aurelius had died, and the troops there acclaimed their commander Avidius Cassius as emperor. When this rumour proved false the crisis quickly passed.
Provinces and frontiers
At Nero’s death the revolt which had broken out in Judaea remained undefeated. The general Vespasian was put in charge of dealing with it, but the outbreak of civil war, and Vespasian’s own successful bid for the throne, meant that no great effort could be made towards ending it.
With Vespasian’s triumph in 69, his eldest son, Titus, who had been left in command against the Jews whilst Vespasian marched on Rome, vigorously prosecuted the war. After a bitter siege he captured Jerusalem in 70 CE, and raised the temple, the centre of the Jewish religion, to the ground. This was not the end of the uprising: weary years of war followed, and the last embers of revolt were finally stamped out in 74 CE, when members of a group of Jewish zealots committed suicide en masse at the fortress of Massada.
Much of Domitian’s reign was taken up with frontier wars. His main achievement was the stabilisation of the Rhine-Danube front after a series of difficult campaigns.
Trajan undertook a major war of conquest beyond the Danube by marching into Dacia (modern Romania and eastern Hungary) and adding it to the empire after a hard-fought war. Trajan commemorated the Dacian war by erecting a huge column in a new forum he built in Rome. This column, which still stands, has realistic depictions of the Roman army on campaign, and is still studied by historians to see how the Roman army of the period was equipped, organized and fought.
Late in his reign Trajan invaded deep into the Parthian empire, intent on defeating that power once and for all. He marched his army right the way through Parthian territory, all the way to the Persian Gulf; but the problems of supply in a hostile land meant that he could not hold the territory, and had to retreat. He died on the way home. Nevertheless, he left the empire larger than it had ever been before.
Hadrian did not continue Trajan’s policy of expansion. Instead he sought to shore up the empire’s defences by organizing the frontiers more carefully. He ordered the building of the long wall that bears his name which runs from coast to coast across northern England; and he strengthened the fortifications along frontiers everywhere.
He was a great traveller, going on tours of inspection to every part of the empire, interesting himself in the welfare of the provincials and the troops.
In 132 a second major Jewish revolt broke out, not only in Judaea but in many cities with Jewish communities in them. This was led by a man called Bar Kochba. It was put down without too much difficulty, and in the aftermath Jews were expelled from Jerusalem and 100 miles around. This was the beginning of their “Diaspora”, their dispersion amongst the nations of the world, without a homeland of their own. This would last until the state of Israel was established in 1947. On the site of the city of Jerusalem Hadrian established a Roman colony.
Antoninus Pius’ reign was one of the most peaceful in Roman history. The only military offensive was into Scotland, where he advanced the Roman frontier to the Firth-Forth line. In Antoninus’ reign, however, the empire was afflicted by a major plague that swept in from the east, and killed millions of people. It seems to have particularly struck the Roman army.
Looking back at that period it is difficult to escape the feeling that a turning point was being reached in the empire’s fortunes. The reign of Antonius’ successor, Marcus Aurelius, was troubled by long wars on the Danube as some barbarian tribes in central Europe sought to migrate across the frontiers into the empire. The Roman defences were hard put to it to contain the threat, and this set the tone for things to come. It may be that the plague had left the army short of manpower. Perhaps significantly Marcus took the step of settling some of the invaders within the empire, in the Balkan provinces, to bolster the population in that region; and deported others to Britain to serve as auxiliaries in the Roman army there. From now on pressure along all the empire’s frontiers would increase, and Roman frontier defences would more and more frequently be breached. The plague would also recur from time to time, keeping population levels somewhat lower than they had been before, and this will have added to the difficulties of mounting an effective defence.
Within the empire itself the period of the Flavians and Five Good Emperors was one of sound government and general peace. With peace came prosperity. The economy expanded to a level which would not be widely seen again in Europe, the Middle East or North Africa until the 17th century. The cities of the empire received lavish endowments from their local elites, with theatres, baths, temples and other public works sprouting up. More and more people became Roman citizens, and the majority of the ruling class of the empire came from the provinces rather than from Roman and Italy. This can be seen in the emperors themselves, who, from the time of Trajan, were seldom Italians.
The sequence of good emperors was brought to an end by the accession to power of Marcus Aurelius’ unworthy son, Commodus (reigned 180-192 CE). He immediately put an end to the interminable fighting on the Danube frontiers by making a treaty with the northern tribes which was widely regarded as a sell-out. On his return to Rome he soon alienated the senate and upper classes by his passion for gladiatorial combat (he even participated himself). He became more and more irrational and dangerous, and was eventually murdered by one of his mistresses.
Commodus’ murder plunged the empire into a second round of civil wars, more than a hundred years after the first. This time these lasted four years, not just one. The an the senate chose to replace Commodus, Pertinax (reigned 192-3), was a stern disciplinarian, and the Praetorian Guard soon killed him. They then put the succession up for auction; but as in 68-9 events had moved away from Rome. Frontier armies began marching on Rome, and civil war followed. It was not until 197 that Septimius Severus, the commander of the Danubian armies, had defeated his rivals and was firmly in power. Severus (reigned 193-211 CE) was a native of North Africa, and his wife was from Syria.
On coming to power Severus discharged the entire Praetorian Guard, and recruited a new one from amongst his own legionaries, most of whom were not Italians. He purged the senate of those who had supported one or other of his rivals. He strengthened the army, raising the pay of the troops considerably (a pay rise for them was in fact long overdue), and he raised three new legions. He ordered all taxes, even from senatorial provinces, to be paid directly into the imperial treasury – the senate’s treasury effectively became little more than the municipal treasury for the city of Rome.
Septimius was succeeded by his two sons, Caracalla and Geta. Caracalla (his official name was Marcus Aurelius Severus Antoninus Augustus; “Caracalla” was a nickname he got from the rough military cloak he wore) soon got rid of his brother and reigned alone (211-217 CE).
Caracalla embarked on a major expedition to Parthia. During it he was murdered by his Praetorian Prefect, Macrinus, who took the purple. He was the first non-senator to do so. He was himself soon murdered, and power passed back to members of the Severan family, with two young men, Elagabalus (218-222) and Alexander Severus (222-237) holding the throne in succession. In both cases, real power lay with their mothers. Elagabalus was of Syrian descent, a priest of a local god whose exotic debaucheries scandalised even Rome. He was soon disposed of. Alexander Severus’s reign saw a measure of stability, and some successes against Rome’s enemies, especially in the east, However his generals were unable to deal effectively with a major Germanic invasion across the Rhine and Danube, and this undermined support for him amongst the troops there. A general mutiny led to his murder, bringing an end to the Severan dynasty.
Politics under the Severi
By this time, power lay with the army: the senate was no more than a cipher which endorsed the will of the troops. However, the long peace of the second century had led to military units being stationed in permanent barracks for generations. Their loyalties had become regional: the troops of the Danubian legions, for example, identified with their own section of the army rather than with the army as a whole. They had little sympathy with the troops far way on the eastern frontier. This trend had actually already been apparent in the events of 68-9 (see above), but were more entrenched now.
Furthermore, there is a sense of growing indiscipline amongst the troops, at all ranks. Three of the five emperors of the Severan period were killed by their own men in the midst of campaigns, Caracalla by a group of senior officers, Macrinus and Alexander Severus by general mutinies. The army may have been the seat of power, but it was an increasingly unstable one.
Away from the frontiers, the provinces remained largely peaceful, and the prosperity of the previous period mostly continued. One trend that was becoming apparent, however, was inflation, caused by regular rounds of official devaluations of the coinage. This was exacerbated by heavier taxation, to pay for the larger and more expensive army. This was becoming a significant problem by the end of the period.
The long-term spread of Roman citizenship reached a conclusion in this period when the emperor Caracalla issued his famous edict granting citizenship to all free men within the Roman empire (212).
All the emperors devoted much attention to the frontiers of the empire, and spent much of their time there. Septimius had to shore up frontiers weakened during the civil wars. He fought a major war against the Parthians, and as usual scored some successes but achieved little of permanence. He spent the last three years waging a costly wear in northern Britain, where he died.
After Septimius Severus’ time, problems along the frontiers increased. Invasions became more frequent, and no emperor was for long able to take his ease in Rome. Some scholars believe that, during the long peace of the second century CE, population pressures within the barbarian world of Germany and central Europe, or some other dynamic, had built up to create an urge to migrate into lands under Roman rule. By the end of the Several period invasions across the Rhine and the Danube were becoming regular events.
At the same time, in the east, a development had taken place which posed another major threat to the empire. Between 222 and 227 CE a new Persian dynasty, the Sasanians, had overthrown the Parthian Arsacids. This replaced a weak, divided regime with a strong, aggressive one. The eastern frontier of the Roman empire was now under graver threat than ever before.
At the same time the plague which had first appeared under Antonius Pius (see above) continued to return from time to time, preventing the manpower of the Roman empire from recovering to pre-plague levels.
Conditions were turning against the Roman Empire.
Articles on Ancient Rome and related topics:
History of ancient Europe at the time when ancient Roman civilization flourished.
History of the ancient Middle East, showing the role the Roman empire played in that region.
Ancient Europe, showing the rise and fall of the Roman empire in the context of European history
The Middle East, showing the impact of the Roman empire on that region
The World when ancient Roman civilization flourished