Final answer:
The Romans were the first civilians to influence the Gauls through conquest and assimilation, resulting in Gauls becoming Roman citizens with significant power and influence.
Step-by-step explanation:
The first civilians to influence the Gauls were the Romans. After the Gauls attacked and sacked Rome in 390 BCE, the Romans fought wars with different Gallic tribes, including the famous Roman-Gallic wars led by Julius Caesar from 58-50 BCE. Despite the conflicts, the Romans eventually conquered Gaul and assimilated the Gauls into Roman society. Gauls became Roman citizens with significant power and influence, even serving as senators. This integration of Gaul into the Roman Empire brought about cultural changes and the adoption of a Roman way of life.