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.
Gaul
The Roman proconsul and general Julius Caesar pushed his army into Gaul in 58 BC, on the pretext of assisting Rome's Gaullish allies against the migrating Helvetii. With the help of various Gallic clans (e.g. the Aedui) he managed to conquer nearly all of Gaul. While their military was just as strong as the Romans, the internal division between the Gallic tribes guaranteed an easy victory for Caesar, and Vercingetorix's attempt to unite the Gauls against Roman invasion came too late. Julius Caesar was checked by Vercingetorix at a siege of Gergovia, a fortified town in the center of Gaul. Caesar's alliances with many Gallic clans broke. Even the Aedui, their most faithful supporters, threw in their lot with the Arverni, but the ever-loyal Remi (best known for its cavalry) and Lingones sent troops to support Caesar. The Germani of the Ubii also sent cavalry, which Caesar equipped with Remi horses. Caesar captured Vercingetorix in the Battle of Alesia, which ended the majority of Gallic resistance to Rome.