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.
Franco-Visigothic Wars
The Franco-Visigothic Wars were a series of wars between the Franks and the Visigoths, but it also involved the Burgundians, the Ostrogoths, and the Romans. Most noteworthy war of the conflict would be the "Second Franco-Visigothic War" that included the famous Battle of Vouillé and resulted in Frankish annexation of most of Southern France.
In 486, Clovis I defeated the Gallo-Romans decisively, impelling the commander, Syagrius to flee to the court of Alaric II. Probably in 487, while Clovis was pillaging the land and besieging the cities that resisted (at least Verdun and Paris) he sent the King of the Visigoths an ultimatum: hand-over Syagrius or risk war. Therefore, instead of aiding the exile, Alaric‒reluctant to combat the Franks‒displayed cowardice and forfeited Syagrius, whom Clovis immediately executed.