Gauls
In 58 BC Julius Caesar launched the Gallic Wars and had conquered the whole of Gaul by 51 BC. He noted that the Gauls (Celtae) were one of the three primary peoples in the area, along with the Aquitanians and the Belgae. Caesar's motivation for the invasion seems to have been his need for gold to pay off his debts and for a successful military expedition to boost his political career. The people of Gaul could provide him with both. So much gold was looted from Gaul that after the war the price of gold fell by as much as 20%. While they were militarily just as brave 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. After the annexation of Gaul a mixed Gallo-Roman culture began to emerge.
Democratic elements of Roman Republic
After Sulla's death, republican rule was more or less restored under Pompey the Great. Despite his popularity, he was faced with two astute political opponents: the immensely wealthy Crassus and Julius Caesar. Rather than coming to blows, the three men reached a political accommodation now known as the First Triumvirate. Caesar was awarded governor of two Gallic provinces (what is now France). He embarked on a campaign of conquest, the Gallic War, which resulted in a huge accession of new territory and vast wealth not to mention an extremely battle hardened army after eight years of fighting the Gauls. Crassus, jealous of Caesar's successes, embarked on a campaign in Parthia, where he was defeated and killed in the Battle of Carrhae. In 50 BC Caesar was recalled to Rome to disband his legions and was put on trial for his war crimes. Caesar, not able to accept this insult after his fantastic conquest, crossed the Rubicon with his loyal Roman legions in 49 BC. Caesar was considered an enemy and traitor of Rome, and he was now matched against the Senate, led by Pompey the Great. This led to a violent Civil War between Caesar and the Republic. The senators and Pompey were no match for Caesar and his veteran legions and this culminated in the Battle of Pharsalus, where Caesar, although outnumbered, destroyed Pompey's legions. Pompey, who had fled to Egypt, was murdered and beheaded.