Gallic Wars
The Gallic Wars were a series of military campaigns waged by the Roman proconsul Julius Caesar against several Gallic tribes. Rome's war against the Gallic tribes lasted from 58 BC to 50 BC and culminated in the decisive Battle of Alesia in 52 BC, in which a complete Roman victory resulted in the expansion of the Roman Republic over the whole of Gaul (mainly present-day France and Belgium). While militarily just as strong as the Romans, the internal division between the Gallic tribes helped ease victory for Caesar, and Vercingetorix's attempt to unite the Gauls against Roman invasion came too late. The wars paved the way for Julius Caesar to become the sole ruler of the Roman Republic.
Celts
Following the Gallic Wars of 58–51 BC, Caesar's "Celtica" formed the main part of Roman Gaul, becoming the province of Gallia Lugdunensis. This territory of the Celtic tribes was bounded on the south by the Garonne and on the north by the Seine and the Marne. The Romans attached large swathes of this region to neighboring provinces Belgica and Aquitania, particularly under Augustus.