Celtic warfare
The "Gallic Wars" were a series of military campaigns waged by the Roman proconsul Julius Caesar against Gallic tribes, lasting from 58 BC to 51 BC. The Romans would also raid Britannia and Germania, but these expeditions never developed into full-scale invasions. The Gallic Wars culminated in the decisive Battle of Alesia in 52 BC, in which a complete Roman victory resulted in the expansion of the Roman Republic over the whole of Gaul. The wars paved the way for Caesar to become the sole ruler of the Roman Republic.
Arverni
The Arverni later played an important role in the Gallic Wars of Julius Caesar from 58 BC to 51 BC. At first the Arvenian nobles tried to avoid confronting Caesar during his early incursions. They executed the leader Celtillus, evidently for trying to gain sovereignty over all the Gauls. In 52 BC, Celtillus' son Vercingetorix rallied his supporters to fight the Romans, but was expelled from Gergovia by the nobles, including his uncle Gobanitio. He then raised a great army in the country, and returned to the city where he ejected his opponents and was declared king. This accomplished, Vercingetorix forged an alliance with at least 15 Gallic tribes, requesting the presence of sons of chiefs to prove their alliance. He then led the majority of the Gauls and won the Gergovia battle against Julius Caesar and his cavalry did marvels in pursuing the Roman troops.
After Julius Caesar saved half of his legions and received food from other Gauls, he went further north to fight weaker opposition. Vercingetorix was defeated by Caesar at the Battle of Alesia, after several months where the legions built 14 ranges of military equipment around the city to lay siege upon the Gallic soldiers. After several weeks of support from the western Gallic people with large numbers of troops coming to support Vercingetorix from outside the city, the Gauls were close to merging the inner and outer forces on 2 occasions. When the outer forces decided to depart, Vercingetorix took the decision to surrender himself to the Romans in order to save the people of Alesia.