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.
Netherlands in the Roman era
During the Gallic Wars, the Belgic area south of the Oude Rijn and west of the Rhine was conquered by Roman forces under Julius Caesar in a series of campaigns from 57 BC to 53 BC. He established the principle that this river, which runs through the Netherlands, defined a natural boundary between Gaul and Germania magna. But the Rhine was not a strong border, and he made it clear that there was a part of Belgic Gaul where many of the local tribes were "Germani cisrhenani", or in other cases, of mixed origin. The approximately 450 years of Roman rule that followed would profoundly change the area that would become the Netherlands. Very often this involved large-scale conflict with the "free Germans" over the Rhine.