Excerpts from Books and Wikipedia
The Gauls were Celtic tribes of Europe west of the Rhine and north of the Alps and Pyrenees. In -52, Vercingetorix united the Gauls to fight the Romans. Caesar besieged Vercingetorix's army in the fortified hill town of Alesia. Surrender was the only option for the Gauls. Survivors of the battle were enslaved. Vercingetorix was paraded in Rome and then killed. [Furtado: 1001 Days] "In the 50s BCE, the campaigns in Gaul, to the north, which were commanded and written up by Caesar, brought several million people under Roman control, not counting the million or so whom he is believed to have left dead in the process." [Beard: SPQR, p. 214]