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.
Marcus Popillius Laenas
Near the end of his consulship with Gnaeus Manlius Capitolinus Imperiosus, the Tarquinians invaded the Roman territories on the Etruscan border, if this Gallic war took place 30 years after the occupation of Rome by the Gauls (in 386/5 BC). Dio Cassius apparently identifies this war with the one in Camillus's fifth dictatorship when the election of the consuls was resumed. Those events took place in 364 BC, about a decade earlier, according to Livy.