Battle of Alesia
Caesar engaged in the Gallic Wars (58–50 BC), which led to his conquest of Gaul beyond Gallia Narbonensis. When the Helvetii, a federation of tribes from what is now Switzerland, planned a migration to the Atlantic coast through Gaul, Caesar went to Geneva and forbade the Helvetii to move into Gaul. While he went to Gallia Cisalpina to collect three other legions, the Helvetii attacked the territories of the Aedui, Ambarri, and Allobroges, three Gallic tribes, which called for Caesar’s help. Caesar and his Gallic allies defeated the Helvetii. The Gallic tribes then asked for Caesar to intervene against an invasion by the Suebi, a Germanic tribe. Caesar defeated the Suebi. In 57 BC he intervened in intra-Gallic conflicts and marched on the Belgae of northern Gaul. From then on he conquered the Gallic peoples one by one. His successes in Gaul brought Caesar political prestige in Rome and great wealth through the spoils of wars and the sale of war captives as slaves.
Battle of Alesia
Alesia proved to be the end of generalized and organized resistance against Caesar's invasion of Gaul and effectively marked the end of the Gallic Wars. In the next year (50 BC) there were mopping-up operations. During the Roman civil wars Gallia was essentially left on its own. Marcus Vipsanius Agrippa became its first governor in 39–38 BC. In 39 BC he settled the Ubians on the west bank of the River Rhine and in 38 BC he suppressed a rebellion in Aquitania. He built a radial network of roads centred on the Gallic capital, Lugdunum (Lyon). Gallia was divided into three Roman provinces; Gallia Aquitania, Gallia Lugdununensis and Gallia Belgica. Only the Arverni kept their independence thanks to their victory against Caesar at the Battle of Gergovia.