Celtic warfare
The "Gallic Wars" were a series of military campaigns waged by the Roman proconsul Julius Caesar against Gallic tribes, lasting from 58 BC to 51 BC. The Romans would also raid Britannia and Germania, but these expeditions never developed into full-scale invasions. The Gallic Wars 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. The wars paved the way for Caesar to become the sole ruler of the Roman Republic.
Wallonia
Julius Caesar conquered Gaul in 57 BC. The Low Countries became part of the larger Gallia Belgica province which originally stretched from southwestern Germany to Normandy and the southern part of the Netherlands. The population of this territory was Celtic with a Germanic influence which was stronger in the north than in the south of the province. Gallia Belgica became progressively romanized. The ancestors of the Walloons became Gallo-Romans and were called the "Walha" by their Germanic neighbours. The "Walha" abandoned their Celtic dialects and started to speak Vulgar Latin.