The earliest recorded inhabitants of the peninsula were the Umbrian tribes living in the Apennine highlands, the Etruscans dominating the north-central areas of the peninsula, the Oscans and Samnites in the southern peninsula, the Messapians in the southeastern heel of the peninsula, the Piceni along the east central coast, and the Latins of the west central area. When Greek colonisation of the southern tip of the peninsula began in the eighth century B.C., no single group dominated the peninsula, although the Etruscans, allied with the Carthaginians, expanded greatly during the initial period of Greek colonisation, coming into conflict with the Greeks over trade through the Straits of Messina. A Greek fleet defeated an allied Etruscan-Carthaginian fleet at the Battle of Alalia in 540 B.C., and Etruscan influence began to decline. When Celtic tribes began increasingly to press from the north, ultimately occupying nearly the entire Po Valley, Etruscan power faced eclipse.
The power of the Roman Republic grew to fill the vacuum. Rome had been politically dominated by Etruscan power for the first centuries of its existence, and ruled by an Etruscan royal family, the Tarquins. Rome shook off Etruscan dominance in 509 B.C., when the last Roman king, Lucius Tarqinius Superbus, was deposed by an alliance of aristocratic Roman families led by Lucius Junius Brutus. The aristocratic families instead established a republican form of government by which the control and honours of government were negotiated annually amongst the founding families--the patrician families. Key to Rome's rise to dominance was its occasionally violent, though largely successful integration of immigrant families into the politics of the city, establishing the plebian families who would come to comprise the majority of Roman citizens. This distinction between patrician and plebian families endured throughout the Republic and was a continuous source of political tension.
Imperfect as it was, the Roman Republic proved better able to respond to the challenges of the Celtic invasion of the peninsula of the early fourth century than its neighbours, and expanded over the next century, absorbing the remnants of the Etruscan city-states, and conquering the Samnite and Oscan tribes to the south. Rome then came into conflict with the Greek city-states in southern Italy, inflamed by the invasion of one of Alexander the Great's successor generals, Pyrrhus of Epirus, who attempted to weld the Greek city-states of western Greece and southern Italy into an empire. Pyrrhus invaded the Italian peninsula at the invitation of the Greek city-state of Tarentum, and fought a five-year campaign against the Roman Republic for dominance in southern Italy and Sicily. The campaigns of Pyrrhus thus brought the conflict of interests of Rome and Carthage in Sicily into sharp focus, prefiguring the First Punic War which would be fought a decade later. Pyrrhus was never defeated by the Romans, but Rome endured repeated defeats and refused to negotiate peace. When Pyrrhus invaded Sicily, Rome seized the opportunity to conquer the Greek city-states of southern Italy, completing its dominance of the Italian peninsula. Ultimately, Pyrrhus, although unbeaten in battle, was politically outmanoeuvred and isolated, forcing his retreat to Greece--the origin of the term "Pyrrhic victory."
Although the Roman Republic emerged from the Pyrrhic War as the dominant military power on the Italian peninsula, its dominance was not unchallenged. Many of the southern cities had capitulated to Rome and maintained a semblance of political independence as client allies in the patron-client relationship so fundamental to Roman thinking. These allies, though expected to follow the orders of the Senate, could demonstrate varying degrees of resistance to Roman rule. When the Carthaginian general Hannibal invaded in 218 B.C., many of the southern cities rose against Rome and allied with Carthage. Putting down these rebellions was the primary object of Roman policy throughout the middle years of the Second Punic War, Rome's armies avoiding direct battle with Hannibal and instead eliminating his allies one by one, in the same manner Pyrrhus had been frustrated.
After the defeat of Hannibal, the restiveness of the southern cities remained a challenge for Rome, breaking out into open rebellion in 91 B.C. in the so-called Social War, in which the rebel cities declared themselves allied into a state they dubbed Italia. By combination of military resolve and political manoeuvre, offering Roman citizenship to cities which did not rebel and to citizens of rebel cities who defected from the rebellion, Rome managed to divide the rebel cities against each other and defeat them in three years. After the Social War, all of the Italian peninsula south of the Rubicon and Arno Rivers was incorporated within the Terra Italia, the land directly owned by Rome or its client-ally city-states
The Social War was therefore the last overt military action in the Italian peninsula before the outbreak of the Third Servile War fifteen years between Rome and any foreign power. The political rivalries between the plebian and patrician classes of Rome itself, and between Rome and the other cities of the Italian peninsula remained, fueling the increasingly bloody civil struggles between political factions which had begun with the assassinations of the Gracchus brothers.
The Third Servile War presented a challenge to Roman supremacy both in its internal social arrangements and in its relations with the other cities of Terra Italia. The reliance on slave labor by all cities of the Italian peninsula made Spartacus a threat to the ruling classes of all of the Italian peninsula, and hampered the efforts of Spartacus to form alliances with the southern cities against Rome.