The consolidation of Rome’s confederacy was rudely interrupted by a Gallic invasion which tempted the Samnites and some of the Etruscans to try conclusions with the Romans once again. New hordes of Celts had crossed the Alps and were unsettling their kinsmen in Cisalpine Gaul. One band swept down through Etruria and even invaded Roman territory in 299, but the main body was fighting the Veneti. The Romans hastily tried to block their southern advance by forming an alliance with the Picentes and capturing Umbrian Nequinum where they founded a Latin colony named Narnia. While Rome was thus preoccupied the Samnites made a final bid for freedom and invaded Lucania. One of the consuls of 298, L. Cornelius Scipio Barbatus, captured Taurasia and Cisauna in south-west Samnium, drove back the Samnites, and exacted hostages from the Lucanians. Meantime his colleague, Cn. Fulvius, attacked northern Samnium where he captured Aufidena, though probably not Bovianum.10 But while the consuls Q. Fabius Rullianus and P. Decius Mus continued the campaign in Samnium during the next two years and captured Murgantia and Romulea in the east, the Samnites, under the leadership of Gellius Egnatius, conceived the bold plan of cooperating with the northern enemies of Rome in a combined attack. In 296, while the storm was gathering, the Samnites raided the Falernian plain, perhaps to distract attention from the north, but they were driven back by Volumnius, and two maritime colonies of Roman citizens were planted at Minturnae and Sinuessa on the Appian Way; Volumnius himself was recalled to support his colleague Appius Claudius in southern Etruria. The next year the Romans hurried their full force through Umbria to prevent the Samnites joining forces with the Gauls. They were too late and their advance guard was defeated near Camerinum. The situation was very grave. It remained to face the allied forces of Samnites, Gauls, and perhaps some Umbrians. A great battle was fought at Sentinum, where the heroic sacrifice of the veteran Decius Mus, the skill of Fabius, and the steadiness of the Roman legions broke the forces of the coalition.11 The disaster of Allia was avenged and the fate of central Italy was sealed. The surviving Gauls and Samnites scattered to their homes, while Fabius marched back through Etruria. The next year the Romans ended the unrest in Etruria by granting a peace for forty years to Volsinii, Perusia and Arretium; as they still had to deal with the Samnites, they were ready to be lenient in Etruria.
But although the coalition was broken and its designer, Gellius Egnatius, lay on the field of Sentinum, the Samnites were far from crushed and succeeded in defeating L. Postumius near Luceria in 294. The Romans were hampered by the visitation of a plague, but in 293 they again took the offensive. The geographical details of the campaign are obscure, but it appears that Sp. Carvilius captured Amiternum to check some Sabine restlessness, while his colleague L. Papirius won a great victory at Aquilonia (Lacedogna) on the Apulian frontier and thus completed the work begun at Sentinum. In the following year a truce was reached with Falerii which had revolted; in 291 L. Postumius stormed Venusia, which controlled the main route from Campania to Apulia, and a large Latin colony was settled there. The Samnites were at last exhausted and peace was re-established in 290. The terms are not preserved, but Rome’s booty was great and the Samnites were mulcted of territory, so that henceforth the Upper and Middle Volturnus replaced the Liris as the dividing line between Rome and Samnium. Although the Samnite League apparently was allowed to continue in existence, the Samnites were no longer friends but ‘allies’, subject to Rome’s demands for troops and obedience in foreign policy. In this same year, 290, M’. Curius Dentatus marched through the territory of the Sabines who were still independent, though doubtless they had become largely Romanized. The whole population was granted civitas sine suffragio and enrolled in the Roman state; not long afterwards it received full franchise. A few square miles of the territory of the Praetuttii, an offshoot of the Sabines, was annexed; a Latin colony was established at Hadria to guard the coast road along the Adriatic.
After a few years of peace the Gauls again gave trouble. The Senones crossed the Apennines and besieged Etruscan Arretium which remained faithful to its alliance with Rome. Caecilius Metellus tried to relieve Arretium and met his death in a battle which cost the Romans some 13,000 men (284). This grave disaster encouraged Etruscan Vulci and Volsinii to revolt, while some Samnites and Lucanians in the south followed suit. But though the Romans had to face danger from several directions, their enemies could not unite to form another coalition. After the Senones had murdered some Roman ambassadors, M’. Curius Dentatus marched into the ager Galliens and drove them out with merciless vigour.12 Their land was annexed and a Roman colony was settled at Sena on the Adriatic. In 283 the Boii took up the cudgels laid down by their kinsmen and joined the Etruscan cities in their revolt. On their southward march they were defeated by Cornelius Dolabella at Lake Vadimo, only fifty miles from Rome. The next year a similar attempt ended in a similar disaster near Populonia; after this the Boii remained quiet for fifty years. Volsinii and Vulci held out till 280 when they were defeated, deprived of part of their territory and enrolled as Rome’s allies. It is possible that the Etruscan towns of Tarquinii, Rusellae, Vetulonia, Populonia, and Volaterrae had participated in the revolt and were now coerced into alliance with Rome. But no sooner were the Gauls defeated and the Etruscans pacified than the Romans were forced to turn to southern Italy where the Samnites and Lucanians were restless, where Thurii appealed for Rome’s help and where in 280 the Greek adventurer, Pyrrhus, King of Epirus, had landed.