Wars of the Roman Empire

At issue: Addition of territory to the Roman Empire, defense of the Roman frontiers

Date: 30 b.c.e.-476 c.e.

Location: Mediterranean, Northwest Europe, Britain, the Balkans, North Africa, Parthia/Persia

Combatants: Romans vs. Spanish, Balkans, Germans, British, Dacians, Parthians, Quadis, Marcomannis, Sāsānids, Persians, Alemanni, Franks, Goths, Heruli, Burgundians, Vandals, Huns, Visigoths, Alans, Suevi

Principal commanders:Roman, Gaius Octavius (Octavian), later known as Augustus (63 b.c.e.-14 c.e.), Claudius (10 b.c.e.-54 c.e.), Nero (37-68 c.e.), Vespasian (9-79 c.e.), Gnaeus Julius Agricola (40-93 c.e.), Trajan (53-117 c.e.), Marcus Aurelius (121-180), Lucius Aurelius Verus (130-169), Lucius Septimus Severus (146-214), Claudius II Gothicus (214-270), Aurelian (c. 215-275), Probus (d. 282), Carus (223-283), Diocletian (245-316), Julian (331-363), Valentinian I (321-375), Valens (328?-378); Persian/Sasanid, Shāpūr I (d. 272); Visigoth, King Alaric (c. 370-410); Vandal, Genseric (d. 477); Hun, Attila (406?-453)

Principal battles: Teutoburg Forest, Ctesiphon, Edessa, Adrianople

Result: The Roman Empire successfully defended its borders against a number of groups until the mid-fifth century, when Germanic groups overpowered the western empire.

Background

After nearly a century of warfare in the Late Republic (146-31 b.c.e.), the Roman army had become a professional fighting force. Military power frequently was used either to acquire or demand political power, and the dependence of powerful generals on their troops was very clear. The wars of the Roman Republic were often motivated by the personal ambitions of generals rather than military emergencies, but with the inauguration of an era of peace beginning in 27 b.c.e., the army had to find a new role to play. Well paid, well fed, and well provided for after retirement, the army was poised to become a major factor in the politics of the Roman Empire.

For ending the civil wars, Gaius Octavius (Octavian) was given the honorary title of Augustus by a grateful Senate. He molded the Roman army into a professional organization with fixed terms and conditions of service, pay rates, promotion procedures, and rank. Augustus also continued the personal relationship between soldiers and generals that had developed since the Late Republic. Soldiers took an oath of loyalty to the emperor and were paid in coins displaying the emperor’s portrait. The soldiers themselves received good pay along with frequent raises and gifts on special occasions. A precedent was set when Augustus’s successor, Tiberius, made a gift of money to the troops upon becoming emperor. Each new emperor was expected to outdo his predecessors in generosity or face the consequences. As no clear system of succession was established in the early empire, transition periods could be dangerous, as would-be emperors competed for the army’s affection and support. The dependence of the emperor on the loyalty of his soldiers, clear to all, was not usually advertised, though a coin of the emperor Claudius depicting him shaking hands with one of his Praetorian guards (imperial bodyguards), is an especially frank portrayal of the relationship between crown and sword.

Action

Augustus added to the empire the greatest amount of territory in Roman history. Spain, long a trouble spot, was pacified by 19 b.c.e. The Alpine regions north of Rome, modern-day Switzerland and Austria, were brought under control by 14 b.c.e. The same year, Rome started wars in the Balkans that ultimately resulted in this region’s addition to the empire. Exotic adventures were also undertaken in the form of campaigns to Arabia and Ethiopia. Augustus’s wars in Germany were seen as a prelude, in a memorable example of Roman geographical ignorance, to his ultimate conquest of China. Campaigns in Germany beyond the Rhine and up to the Elbe were fairly successful until a terrible defeat in 9 c.e. in the Teutoburg Forest. In the murky darkness, three legions under the command of Publius Quintilius Varus were completely wiped out, leaving Augustus (according to legend) to wander the palace at night screaming, “Varus, give me back my legions!” Less legendary, though not entirely certain, is the advice that Augustus supposedly left his successors, that they were not to extend the empire beyond its existing limits. For most of the first century c.e. this policy was maintained, with the notable exception of the invasion of Britain by Claudius I. Claudius’s motives for conquest were most likely military glory, as Britain offered no strategic value other than the fact that its pacification might keep neighboring Gaul safer.

Between 68 and 69 c.e., known as the year of the four emperors, the Roman Empire experienced a brief civil war. In 68 c.e., distressed at the conduct of the flamboyant and cruel Nero, Gaius Julius Vindex, the governor of Gallia Lugdunensis (southern France), revolted against him. Nero’s subsequent suicide left no clear successor. Into this vacuum stepped the ultimate source of imperial authority, the legions. The following year, Servius Sulpicius Galba, a governor in Spain, was hailed as emperor by his troops. Only months after his elevation and arrival in Rome, he was killed by his own Praetorian guards in favor of Nero’s friend Marcus Salvus Otho, a man with deeper pockets than the frugal Galba. Meanwhile, the governor of Lower Germany, Aulus Vitellius, revolted, and the resulting clash between the armies of Otho and Vitellius devastated the Italian countryside. Vitellius’s triumph over Otho was short-lived, however, as Vespasian, the governor of Syria, was saluted as emperor by his troops. The legions of Pannonia (modern Croatia) supported Vespasian and invaded Italy, eventually reaching Rome where Vitellius had been killed amid urban violence and his own soldiers’ desertion.

Relatively speaking, the succession struggles were brief, if bloody, and did not result in any long-term interruption of the Roman peace. Under the reigns of Vespasian, Titus, and Domitian, the principal areas of conflict were Germany and Britain. Roman historian Tacitus’s biography of Gnaeus Julius Agricola, governor of Britain from 77 to 84 c.e., describes conditions in Britain. Agricola extended Roman control into northern England and southern Scotland, and mounted an expedition to circumnavigate the island.

On the whole, the military situation was fairly calm throughout the empire, save for a serious revolt in Germany under Domitian, until Trajan launched two major campaigns that considerably extended the frontiers of the empire. His wars against Dacia (modern Romania) were fought in 101-102 and 105-106. He took personal command of his legions and marched with them. The Dacian Wars, images of which can still be seen on Trajan’s Column in Rome, were ultimately successful and added to the empire a significant amount of territory beyond the Danube. Trajan’s other major military effort was a war against the Parthians in 113-117, which expanded the empire to its greatest territorial extent. Taking advantage of internal conflicts within the Parthian Empire, Trajan captured the capital of Ctesiphon in 116. However, the new conquests were abandoned by his successor Hadrian.

After Trajan’s adventures, no major wars were fought against external enemies until the reign of Marcus Aurelius, when ominous developments began on both the Parthian and northern frontiers. The Parthian War (162-165), conducted chiefly by Marcus’s co-emperor Lucius Aurelius Verus, were defensive, and it is noteworthy that despite his success, Verus did not try to replicate the feats of Trajan. More serious were the wars against the Quadi and the Marcomanni, Germanic tribes who invaded the empire from across the Danube. One reason for the fragility of the frontiers was a shortage of troops, many of which had been sent to fight in Parthia. Though weakened by plague brought back from Parthia by Verus’s troops, the army eventually rallied under Marcus’s leadership. The Marcomannic Wars (166-173, 173-180), however, were long and costly and a mere prelude to the more serious conflicts that were to follow in the coming century along Rome’s northern frontiers. Moreover, the wars with the Marcomanni and the Parthians had demonstrated a major problem in Roman frontier defense: simultaneous crises on the empire’s vast frontiers.

Lucius Septimus Severus came to power in 193 after another round of civil wars following the death of the emperor Commodus. Severus, who rose to power on the shoulders of his legions, was keenly aware of the importance of the army, and he increased the army’s pay for the first time since 84 c.e. Wars in Parthia (197-199) extended Roman territory, and campaigns in Britain (208-211) pushed the frontier temporarily northward.

Ironically, Severus’s Parthian campaigns would come back to haunt the Romans. The Parthian state, weakened after the Roman wars, fell victim in 224 to a rebellion led by Ardashīr, whose Sāsānid Dynasty sought to resurrect the ancient Persian Empire in all its glory. At the same time, the Volkerwanderung (“Movement of the Peoples”) was changing the character of Rome’s northern frontiers. Frequent wars were fought with the Persians and the various Germanic tribes, among them the Alemanni, Franks, and Goths. The Germanic invasions were especially destructive along the Danube frontier, where in 251, the Emperor Decius was killed in battle against the Goths; his body was never found. The Goths eventually went on to plunder Greece and Asia Minor in 252-253, 256, and 258. The Franks and Alemanni pillaged towns in Gaul. The wealthy eastern provinces were also affected by new Persian invasions, culminating in the defeat and capture of the emperor Valerian by the Persian king Shāpūr I at the Battle of Edessa (258-259). Separate empires, declaring their full independence from Rome, emerged in Gaul and Syria. Roman imperial fortunes seemed to have reached their lowest ebb. Gallienus, who came to power in 253, acquiesced in the division of the Roman Empire, for it allowed him to focus on the threatened frontiers of northern Italy and the Danube region. He handled the various threats quite effectively, but in 267, new invasions by the Heruli (a Germanic people) resulted in the sacking of several Greek cities including Athens.

The military crisis of the mid-third century was accompanied by political crisis. From 235 to 284, about thirty emperors—eighteen of which were “legitimate” emperors—vied for the throne. Nearly all the emperors in this period died violent deaths. Under the severe constraints of warfare and the often ineffective attempts by the emperors to protect the frontiers, army discipline broke down. Soldiers frequently hailed their own generals as emperor. These “emperors” would accept their prize, distribute the anticipated bonuses to their armies, then set off for Rome to take on the current emperor. These civil struggles left the frontiers bereft of troops and vulnerable to attack.

A series of tough emperors who rose through the ranks of the army—Claudius II Gothicus, Aurelian, Probus, and Carus—steadily defeated the Germanic invaders. Claudius and Aurelian both fought off invasions of Italy by the Alemanni and Goths. The gravity of the emergency is demonstrated by the construction of the Aurelian Wall around Rome (271-276), the first such defensive wall built since the fourth century b.c.e. Aurelian also destroyed the breakaway empires in Gaul and Syria, thus restoring the territorial unity of the empire. Dacia, however, was abandoned by Aurelian in order to shorten the defensive line in the Danube region. Probus won major victories against the Alemanni, Franks, Burgundians, and Vandals in Gaul and Raetia (present-day Switzerland) from 277 to 280. Carus marched against the Persians and captured Ctesiphon but was killed (like so many of his predecessors) by treachery within his own ranks.

In 284, Diocletian ascended to the throne and established a clear system of succession to eliminate the potential for rebellions that had characterized the previous fifty years. His system, known as the Tetrarchy, divided the empire first into halves, with his colleague Maximian emperor in the west and Diocletian in the east. Diocletian further divided the imperial power by appointing two assistants: Constantius I in the west and Galerius in the east. All four were busy campaigning during their reigns. Constantius subdued the rebellious Carausius and Allectus in Britain by 296. Maximian defended the Rhine frontier and crushed revolts in Gaul and North Africa. Diocletian fought successful campaigns against the Sarmatians and the Carpi in the Danube region and defeated them by 296. He also crushed a revolt in Egypt in 297. Galerius won substantial territories from the Persians in 298 after a very successful campaign that kept the frontier between the two empires basically stable for the next sixty years.

The major areas of military operation in the fourth century were on the Rhine, Danube, and Persian frontiers. The empire’s wars in this period are described in the historical work of Ammianus Marcellinus, who served with the emperor Julian on his campaigns in Gaul and Persia and provides a rare firsthand account of camp life and battle. Julian and his successor Valentinian I fought a series of ultimately successful campaigns in Gaul against the Alemanni. The amount of effort, in terms of military operations and building activity along the frontiers, testifies to both the efficiency of the imperial military administration in a time of supposed “decline” as well as to the severity and seeming endlessness of frontier crises.

Julian’s uncle, the Emperor Constantine, was about to lead an invasion of Persia when he died in 337. Constantine, a Christian, had given the religion favored status within the empire. Julian, however, rejected Christianity in favor of paganism, and perhaps chose to undertake an invasion of Persia in imitation of Constantine, thus demonstrating the strength and vitality of the traditional gods. In any case, the expedition proved a disaster. Julian was killed, and his successor Jovian was forced to sign a humiliating peace with Persia that effectively negated the gains of Galerius in 298.

On the Danube frontier, the crisis was even greater and ultimately more destructive. Under pressure from the Huns, who were pushing westward, the Visigoths negotiated entry into the Roman Empire as settlers but met with horrendous abuse and mistreatment at the hands of Roman officials. The Visigoths revolted, and on August 9, 378, engaged in battle with a Roman army under the command of the emperor Valens outside the city of Adrianople. The battle was the worst defeat the Roman army had suffered since Cannae in 216 b.c.e. Two-thirds of Valens’s army was annihilated, and the emperor was killed and his body never found. Ammianus describes the scene in gruesome detail and fittingly closes his history with this momentous defeat. After Adrianople, the Visigoths were essentially unopposed and gradually migrated westward to the less urbanized parts of the empire.

The empire was formally divided after the death of Theodosius I in 395 into eastern and western halves. The Eastern Roman Empire, with its greater number of cities and shorter frontiers, was better able to withstand incursions by barbaric tribes penetrating Roman territory across the Danube. The Western Roman Empire, now governed from the heavily fortified city of Ravenna in northern Italy, was less able to resist the frequent invasions, the greatest of which was made by the Vandals, Alans, and Suevi, who crossed the frozen Rhine into Gaul on the last night of 406. How devastating these invasions were is a matter of controversy. Although violence and destruction abounded, the carnage was not uniform nor was it was catastrophic. Many wealthy landholders were able to buy off potential pillagers and send them on their way. However, the depredations perpetrated by the Visigoths, for example, on the city of Rome in 410 resounded throughout the Mediterranean. For three days, the warriors of King Alaric plundered the capital. A much worse pillaging was to come in 455 when seagoing Vandals under their king Genseric, sailing from their new home in North Africa, raided and looted the city once again.

The greatest threat to the Western Roman Empire, however, was the presence of the Huns. A Turkic people who were excellent horsemen as well as foot soldiers, they struck terror into the hearts of urbanized Romans. In 451, a combined Roman and Visigothic force united to defeat the Huns and their king Attila at the Battle of Châlons in Gaul. It proved to be a temporary respite; the Huns invaded Italy in 453, and only Attila’s death and the presence of plague in his army prevented what could have been a catastrophe.

By the mid-fifth century, the Roman army was no longer able to maintain the territorial integrity of the empire in the west, and portions of Gaul, Spain, and Africa came under the direct control of Germanic kings. Britain had been abandoned in the early fifth century to meet the Vandal threat on the continent. The last Roman emperors in the west were military puppets, manipulated by skilled Germanic generals such as Stilicho and Aetius. The last emperor, twelve-year-old Romulus Augustulus (“the little Augustus”), was deposed and packed off to southern Italy in 476 by the general Odoacer, who tired of the charade and crowned himself king of Italy. The Western Roman Empire was gone.

Aftermath

The demise of the Western Roman Empire meant the end of political unity, as Germanic kingdoms grew out of the ruins of a once-united realm. Roman culture continued to exist but gradually became blended with the culture of the new Germanic overlords. In stark contrast to the western empire, the Eastern Roman Empire remained essentially intact. Its frontiers were adequately defended and its cities well fortified and able to withstand sieges. Peace with Persia, though fragile, kept the eastern frontiers quiet until the reign of Justinian I in the sixth century. A “Roman” emperor ruled in Constantinople, the eastern empire capital, until 1453, but the Roman character of the eastern empire was so changed by the time of Justinian that from his reign on, the empire is generally regarded as the Byzantine Empire.

Bibliography

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Ferrill, Arther. The Fall of the Roman Empire: The Military Explanation. London: Thames & Hudson, 1986.

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Isaac, Benjamin. The Limits of Empire: The Roman Army in the East. Rev. ed. Oxford, England: Oxford University Press, 1993.

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