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.
Wallonia
Julius Caesar conquered Gaul in 57 BC. The Low Countries became part of the larger Gallia Belgica province which originally stretched from southwestern Germany to Normandy and the southern part of the Netherlands. The population of this territory was Celtic with a Germanic influence which was stronger in the north than in the south of the province. Gallia Belgica became progressively romanized. The ancestors of the Walloons became Gallo-Romans and were called the "Walha" by their Germanic neighbours. The "Walha" abandoned their Celtic dialects and started to speak Vulgar Latin.