Territorial Expansion of the Roman World

The Roman Empire at its greatest extent under Trajan in 116 AD

Expansion during the Early Roman Republic (509 – 265 B.C.E.)

The Italian peninsula was inhabited principally by several native tribes before the Greeks settled there and the Etruscans rose to prominence sometime after 800 B.C.E. The Greeks founded several city-states in the south of the peninsula and in Sicily, and the Etruscans rose to power on the western coast where they brought their culture to the Latin peoples settled in small villages along the Tiber River. Here, three centuries later, a prosperous urban centre called Rome would emerge. Rome flourished under the Etruscans but the Latin population resented sovereign Etruscan rule and joined with other indigenous tribes in a rebellion. The revolution of 509 B.C.E., which dethroned the Etruscan king and drove his people from Rome, marks the beginning of the Roman Republic that would see Rome rise to dominance around the Mediterranean. The Roman Republic continued until 31 B.C.E. when it was replaced by the Roman Empire that would last well into the fifth century C.E.

Beginning in 437 B.C.E., with the defeat and annexation of neighbouring towns, and over the course of the next two centuries, Rome gradually expanded its territory and political dominance over the peninsula. Even though Rome had a superior army, it was not immune to attack. In 390 B.C.E, Celts swept down from the Po River valley and captured and sacked Rome. Recovering quickly from this defeat, Rome went on to successful future campaigns and by 235 B.C.E., after almost incessant warfare with its neighbouring Etruscan and Italian city-states, all of the Italian peninsula south of the Po Valley was conquered.

Rome’s successful conquest of the Italian peninsula created a strong military ethos and provided the Roman state with considerable manpower. When the unification of the peninsula brought Rome into conflict with Carthage, a major power that monopolized western Mediterranean trade from Northern Africa, Rome was inclined to enter into war. Rome built up a fleet and in the three Punic Wars between 264 and 146 B.C.E., defeated the Carthaginian navy. From Carthage, Rome acquired the territories of Sicily, Sardinia, Corsica, Spain and Numidia (modern Tunisia) and extended its dominance to all of the western Mediterranean.

Expansion into the eastern Mediterranean was achieved between 230 and 133 B.C.E. Initially, Rome intervened in the east to protect itself from possible threat and to protect the Greek city-states from territorial advances. Rome did not annex any territory at first, treating Greece and Asia Minor as protectorates, but when the stability of the Aegean was again threatened in 179 B.C.E., Rome changed its policy and conquered Macedon. The Romans opted for direct rule in the east in part because successful warfare brought vast riches for the state, and honour and power to military leaders. Complete Roman rule was established in the east in 133 B.C.E. when flourishing Asia Minor was bequeathed to Rome.

Rome’s success in its territorial expansion can be credited to its military superiority and to its policy of absorbing conquered peoples. Rome did not enforce absolute subjection, for local governments, traditions and laws were respected, and conquered subjects were encouraged to identify their well-being with Roman success. Rome achieved this by granting full rights of citizenship to its nearest neighbours, and partial citizenship or ally status to other subjects. All of Rome’s subjects had to pay taxes and provide military service in wartime, but it was understood in these arrangements that partial citizenship and ally status would eventually result in full citizenship, especially for those who became Romanized.

Expansion during the Late Roman Republic (133 – 31 B.C.E.)

Military glory was highly prized in Rome. Wars continued to be fought and the frontiers of the Roman World were gradually extended outward as a result. During the last century of the Republic, Roman generals won victories in northern Africa and in southern France, where upon a Roman colony was settled in Narbonne and a road built to link Italy with Spain. By 80 B.C.E., Syria was conquered and the province of Asia was established. After 66 B.C.E., additional territory was conquered further east where new provinces were founded and Jerusalem was conquered. In areas where Roman expansion seemed problematic, client kingdoms were established. In exchange for relative autonomy, these client states helped defend the empire from foreign attack. At a later date, after years of living under Roman dominion, these client kingdoms would be easily incorporated into the empire without a war having been waged. Between 58 and 50 B.C.E., Julius Caesar defeated the Celtic Gauls, thus conquering a large area corrsponding to modern France and Belgium. Gaul would be divided into four provinces: Narbonensis, Aquitania, Belgica and Lugdunensis. Caesar’s campaigns spread Roman language and civilization far beyond the Italian peninsula.

Expansion during the Early Roman Empire (31 B.C.E. – C.E. 180)

When the Roman Republic came to an end, the territorial frontiers of the Roman state were poorly defined, but Augustus, Rome’s first emperor (r. 27 B.C.E. – C.E. 14), led campaigns that extended Roman influence to the natural boundaries defined by desert, sea, ocean and river. His armies conquered all of North Africa, and territory reaching as far east as the Red Sea and the Black Sea, as far west as the Atlantic and north to the great rivers of central Europe: the Rhine and the Danube. These rivers provided the northern frontier to the new provinces of Raetia, Noricum and Pannonia that today encompass Switzerland and Austria. To the east, the Danube provided the northern limit to the new provinces of Pannonia and Moesia that encompass parts of present-day Slovenia, Hungary and Bulgaria. The Rhine and the Danube, the northern frontier of the Roman World, would prove to be the fatal weak link in Rome’s defences by the fifth century. As early as C.E. 9, when attempting to make territorial gains north of this frontier, Augustus suffered the only defeat of his many military campaigns; German tribes annihilated three Roman legions in the Teutoburg Forest in northwestern Germany. Augustus, now at the end of his reign, decided against further expansion and urged his successor to do the same.

Although Augustus’ advice was heeded for several years, the next century did see the incorporation of client kingdoms, and the successful annexation of Britain in C.E. 43 and of the Agri Decumates, a triangle of territory at the junction of the Rhine and Danube frontiers, in C.E. 74. Not all was well within the empire, however, and revolts and uprisings within Roman provinces forced Rome to redirect some of its troops from the Rhine and Danube frontiers to the rebellious areas. This move left the northern frontiers ill-defended and open to border raids. Rome responded to this threat by strengthening the frontier defences with additional legions.

Under Emperor Trajan (r. 98 – 117), the Roman state reached its greatest extent. Client kingdoms on the eastern frontier were incorporated and new provinces created. As well, Dacia was conquered so as to distance hostile tribes from the dangerous Danube frontier. Emperor Hadrian (r. 117 – 138) opposed territorial expansion but kept the army at full strength, and built fortified boundaries across Britain (known thereafter as Hadrian’s Wall) and between the Rhine and Danube Rivers. His next two successors faced rebellions in many of the borderlands and terrible assaults against the frontiers. The Danube frontier collapsed and Germanic invaders, pressed on from behind by the southward migration of other Germanic tribes, crossed the northern provinces and raided northern Italy. When the frontiers were once again secure, some invaders were settled along the Danube with land grants in exchange for military service in defence of the Empire’s frontiers.

Territorial Defence during the Late Roman Empire (C.E. 180 – 476)

The third century marks a clear reversal as Rome’s military policy became one of defence rather than territorial expansion. As the century progressed, the northern frontier was seriously weakened as it fell victim to the increasingly heavy migration of German tribes from northern Europe. The western and eastern halves of the empire were attacked by successive waves of Goths, Vandals and Burgundians. Invaders overwhelmed the frontiers, and the borderlands were abandoned by the Roman troops. Many regions were lost to the invaders, and cities and towns were pillaged or destroyed in both the west and the east; Athens was taken and plundered in C.E. 267. During the late third and early fourth century centuries, the borders were strenghtened and the number of legions increased, but these efforts ultimately failed as wave after wave of Germanic peoples invaded and settled in western Europe in the fifth century. Symbolic was the sack of Rome in C.E. 410.