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.
Military campaigns of Julius Caesar
Plutarch claimed that the army had fought against three million men in the course of the Gallic Wars, of whom 1 million died, and another million were enslaved. 300 tribes were subjugated and 800 cities were destroyed. Almost the entire population of the city of Avaricum (Bourges) (40,000 in all) was slaughtered. Julius Caesar reports that 368,000 of the Helvetii left home, of whom 92,000 could bear arms, and only 110,000 returned after the campaign. However, in view of the difficulty of finding accurate counts in the first place, Caesar's propagandistic purposes, and the common gross exaggeration of numbers in ancient texts, the totals of enemy combatants in particular are likely to be far too high. Furger-Gunti considers an army of more than 60,000 fighting Helvetii extremely unlikely in the view of the tactics described, and assumes the actual numbers to have been around 40,000 warriors out of a total of 160,000 emigrants. Delbrück suggests an even lower number of 100,000 people, out of which only 16,000 were fighters, which would make the Celtic force about half the size of the Roman body of ca. 30,000.. men.