With the expulsion of the Etruscan Kings and the establishment of the Republican system firmly rooted, Rome soon turned its attention to regional dominance and expansion. Rome ineherited leadership from the Etruscans and was already the dominant player in the Latium region by 509 BC. A treaty with Carthage at this time essentially recognized Roman authority and influence over the other Latin states. These city states had formed and alliance called the Latin League, intended to provide enough mutual strength and unity of interests to treat with Rome as equals. There is some conflicting evidence on Roman inclusion within this league, but there is no doubt that within these formative stages, they were mostly at odds.
From the early Sixth Century BC on, the Latin League was a cooperation of states sharing common interests such as religious worship and defense of the region from invasion. Latium was fertile, wealthy, had access to the sea and was therefore an inviting target to enemies such as the Etruscans, Volscians, and the Aequians. The cities of the Latin league shared commercial treaties and provided rights of commerce, inter-marriage and settlement to its citizens. It was these rights that formed the basic of the Latin rights that were to play such an important role in later Roman politics and treaties.
When Etruscan rule over Rome, and the other states in Latium, was broken, the League vied with each other for dominance. The balance of power shifted often between Rome and other influential cities like Alba Longa and Lavinium. By 496 BC these power gambits turned to war when Lavinium broke its alliance with Rome in an attempt to assume power. Members of the League united with Lavinium and Tusculum and moved against Rome. At the battle of Lake Regillus, Rome claimed victory over the combined might of her neighbors. Whether this victory was outright, or for all intensive purposes, a stalemate, its significance was that it proved Rome's ability to stand against the combined might of her neighbors.
Within a few years (493 BC) the war drew to a close, with the Latin League claiming independence from Rome. The foedus Cassianum (treaty of Cassius), ensured this independence but placed Rome virtually on equal status with all the members of the Latin League combined. Alliances continued to form and shift over the next century but external pressures, mainly from the Umbrians (Volsci and Aequi) and Sabines forced Rome's immediate neighbors into closer ties. These alliances essentially eliminated this sense of independence and would eventually lead to the absorption of cities and people into the Roman sphere of influence.
The 5th century BC was a time of nearly constant expansion among the Oscan-Umbrian hill peoples. One of these tribes, the Hernicii, was highly adapted to Latin culture and customs. With the pressure from the Aequi and Volsci, the Hernici joined the mutual protection treaty between the Romans and Latins in 486 BC. The armies defending Latium consisted of Romans, Latins and Hernici. As time passed and the alliance grew more essential to survival, the Hernici were soon absorbed into the Latin culture and, as a result, little is known of them.
Through the middle of the century virtually every year was wrought with conflicts.
To the east of Latium, the Latin towns Tibur and Praeneste were threatened by the Aequi. The Aequi were responsible for numerous raids and attacks including purportedly reaching the gates of Rome on several occasions. Details of this time period are sketchy at best, and we rely on the not so reliable reports of the ancients (ie Livy). These towns disappear from recorded history about this time and it can be assumed that the invasions were responsible. In 458, a Roman army was supposedly eliminated at the Agidus pass, which leads into Latium east of Tusculum. In response, L. Quinctius Cincinnatus was appointed dictator and is said to have won a decisive victory over the Aequi. The Aequi, however, were not so easily defeated and were back waging war within a couple of years.
At this time, the Volsci were in control of much of southern Latium (Cora, Velitrae, Satricum, Antium), and pressured the Latins from there. Under the leadership of the legendary Roman renegade Coriolanus, they, much like the Aequi were said to have reached Rome itself. The decisive battle between the Latins and these Umbrian invaders appears to have been fought in 431 BC. The Romans, under the command of A. Postumius Tubertus, again met the Aequi at the Algidus pass, but were this time victorious. With this victory the Romans opened and aggressive offensive which the Umbrian tribe were unable to withstand forever. By the 390s the Romans and Latins had regained control of the plains and relegated the Aequi and Volsci to the western highlands. The Volsci were finally defeated with the capture of the port of Antium in 377 BC. The Aequi seem to be eliminated from history as a separate entity within this same time frame.
To the northeast of Rome, the territory between the Tiber and Anio was constantly pressured by the Sabines. Historical accounts of the Roman relationship with these people are mixed. A Sabine invasion is said to have seized Rome in 460 BC, but after a major victory for Rome in 449 the Sabines fall from the annals of history for nearly 2 centuries. They, like other neighbors were eventually absorbed into Roman culture and became a part of the growing city. As an example, one such Sabine zealously allied with Rome. In contrast to their invading cousins, and during open conflict, they sought and gained permission to move their entire populace onto Roman territory and become Romans. Among these immigrants were the Attus Clausus, later the Roman Gens Claudian, which evolved into one of Rome's elite and highly influential families.
As stated previously, with the victory over the Umbrians, the military policy of Rome became more aggressive in the 60 years between 449 and 390 BC. The Etruscans, especially the city of Veii, remained a constant source of strife. By 396 BC, in large part thanks to Gallic invasions, the Etruscans were weak and the door to their conquest was opened. But the Gauls were on the move from the north and disastrous conflict would be in store. Further Roman expansion to the south was to be met by the Samnites in a series of several wars. In the 300 years since her founding Rome had yet to firmly secure its own region of Latium and still faced considerable challenges ahead.