Over the course of nearly four centuries, the Roman Republic fought a series of wars against various Celtic tribes, whom they collectively described as Galli, or Gauls. Among the principal Gallic peoples described as antagonists by Greek and Roman writers were the Senones, Insubres, Boii, and Gaesatae.
The Romans first came into conflict with Gauls who entered Italy from the north. Some of these settled in the lands immediately south of the Alps, which became known as Cisalpine Gaul: "Gaul this side of the Alps". Gaulish armies, some perhaps fighting as mercenaries in the service of the cities of Magna Graecia, plundered territory in Etruria and Latium during the fourth century, famously sacking Rome circa 390 BC.
Following the Samnite Wars and the Punic Wars, in which Gallic forces sometimes made common cause with Rome's enemies, the Romans found themselves in near-total control of Italy, including Cisalpine Gaul. As they consolidated their gains, they came into conflict with Gallic tribes on the borders of their growing empire, and subsequent conflicts occurred in and beyond the Alps. In the first century BC, Caesar's campaigns in Gaul brought most of the Gallic territory in western Europe under Roman control.
