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.
Gauls
By the 5th century BC, the tribes later called Gauls had migrated from Central France to the Mediterranean coast. Gallic invaders settled the Po Valley in the 4th century BC, defeated Roman forces in a battle under Brennus in 390 BC and raided Italy as far as Sicily.