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.
Gauls
After more than a century of warfare, the Cisalpine Gauls were subdued by the Romans in the early 2nd century BC. The Transalpine Gauls continued to thrive for another century, and joined the Germanic Cimbri and Teutones in the Cimbrian War, where they defeated and killed a Roman consul at Burdigala in 107 BC, and later became prominent among the rebelling gladiators in the Third Servile War. The Gauls were finally conquered by Julius Caesar in the 50s BC despite a rebellion by the Arvernian chieftain Vercingetorix. During the Roman period the Gauls became assimilated into Gallo-Roman culture and by expanding Germanic tribes. During the crisis of the third century, there was briefly a breakaway Gallic Empire founded by the Batavian general Postumus.