The rebellion against Rome by the Gallic tribes started with a massacre of Romans in a hillfort town which signaled to other tribes to join the fight. As the rebellion gained steam, even previously friendly tribes of Rome sided with the Gallic tribes.
Historian Mike Duncan talks about the logistical challenges the Belgians faced during their revolution and how Julius Caesar was able to take advantage of the large, decentralized barbarian armies using his more centralized Roman logistical infrastructure in the Gallic Wars.
Caesar gives a long speech, written to demonstrate the extremities that people will go to during war. The people of Alesia, an entire pan-tribal group, are trapped inside a hillfort without the knowledge of any news or reinforcement, running low on food and having a hardcore debate amongst themselves, with some considering to resort to cannibalism as a last resort.
Caesar's conquest of Avaricum resulted in the death of nearly the entire population of 40,000 people, with only 800 survivors. It is unclear whether this was part of Caesar's plan, but he strategically chose who would be shown clemency and who would be decimated.
In 52 BCE, Julius Caesar faces one of the toughest challenges of his life as he tries to suppress a rebellion by Celtic tribes in Gaul. The battles at Gergovia and Vercingetorix's growing military victories tip the scales in the tribe's favor.
Caesar faces a critical battle against the Belgians and Nervians, where he risks losing his troops and the fate of the Roman Republic. He maximizes his chances of becoming a casualty by helping the units most threatened.