Rome had never been exposed to greater danger than at this time. Those who had been her bravest defenders now rose against her; and she would probably have perished had the whole Italian people taken part in the war. But the insurrection was confined almost exclusively to the Sabellians and their kindred races. The Etruscans and Umbrians stood aloof, while the Sabines, Volscians, and other tribes who already possessed the Roman franchise, supported the Republic, and furnished the materials of her armies. The nations which composed the formidable conspiracy against Rome were eight in number - the Marsians, Pelignians, Marrucinians, Vestinians, Picentines, Samnites, Apulians, and Lucanians. Of these the Marsians were particularly distinguished for their courage and skill in war; and from the prominent part which they took in the struggle, it was frequently termed the Marsic as well as the Social War.
The war broke out at Asculum in Picenum. The Proconsul Q. Servilius, who had the charge of this part of Italy, hearing that the inhabitants of Asculum were organizing a revolt, entered the town, and endeavored to persuade them to lay aside their hostile intentions. But he was murdered, together with his legate, by the exasperated citizens, and all the Romans in the place were likewise put to death. The insurrection now became general. The Allies entered upon the war with feelings of bitter hatred against their former rulers. They resolved to destroy Rome, and fixed upon Corfinium, a strong city of the Peligni, to which they gave the name of Italica, as the new capital of the Italian Confederation. The government of the new Republic was borrowed from that of Rome. It was to have two Consuls, twelve Prætors, and a Senate of 500 members. Q. Pompædius Silo, a Marsian, one of the chief instigators of the war, and C. Papius Mutilus, a Samnite, who cherished the hereditary hatred of his countrymen against the Romans, were chosen Consuls. Under them were many able lieutenants, who had learned the art of war under the best Roman generals. The soldiers had also served, in the Roman armies, and were armed and disciplined in the same way, so that the contest partook of all the characters of a civil war. But the Romans had the great advantage which a single state always possesses over a confederation.
Of the details of the war our information is meagre and imperfect. But in the military operations we clearly see that the Allies formed two principal groups: the one composed of the Marsians, with their neighbors the Marrucinians, Pelignians, Vestinians, and Picentines; the other of the Samnites, with the Lucanians and Apulians. The two Consuls, L. Julius Cæsar and P. Rutilius Lupus, took the field with powerful armies, and under them served Marius, Sulla, and the most experienced generals of the time. The Romans were fully aware of the formidable nature of the struggle, which was one for existence, and not for victory. In the first campaign the advantage was on the side of the Allies. The Samnites, under their Consul Papius, overran Campania, took most of the towns, and laid siege to Acerræ, into which Cæsar threw himself. Pompædius Silo was still more successful. He defeated the Roman Consul P. Rutilius Lupus with great slaughter, Rutilius himself being slain in the battle. This disaster was to some extent repaired by Marius, who commanded a separate army in the neighborhood, and compelled the victorious Allies to retire. The old general then intrenched himself in a fortified camp, and neither the stratagems nor the taunts of the Samnites could entice him from his advantageous position. "If you are a great general," said Pompædius, "come down and fight;" to which the veteran replied, "Nay, do you, if you are a great general, compel me to fight against my will" The Romans considered that Marius was over-cautious and too slow; and Plutarch says that his age and corpulence rendered him incapable of enduring the fatigue of very active service. But it is more probable that he was not very willing to destroy the Allies, who had been among his most active partisans, and to whom he still looked for support in his future struggles with the Nobility.
The Romans now saw the necessity of making some concessions. The Lex Julia, proposed by the Consul Julius Cæsar, granted the franchise to all the Latin colonies, and to those of the Allies who had remained faithful to Rome, or had laid down their arms. The effects of this concession were immediately seen. Several of the Allies hastened to avail themselves of it, and disunion and distrust were produced among the rest.
The next campaign (B.C. 89) was decidedly favorable to the Romans. The Consuls were Cn. Pompeius Strabo, the father of the celebrated Triumvir, and L. Porcius Cato. The latter, it is true, was slain at the commencement of the campaign; but his loss was more than compensated by his lieutenant Sulla obtaining, in consequence, the supreme command. He carried on the war with the utmost vigor, and completely eclipsed his old commander Marius. He drove the enemy out of Campania, subdued the Hirpini, and then penetrated into the very heart of Samnium. Here he defeated Papius Mutilus, the Samnite Consul, and followed up his victory by the capture of the strong town of Bovianum.
Meanwhile Pompeius Strabo had been equally successful in the north. Asculum was reduced after a long and obstinate siege. The Marrucinians, Vestinians, Pelignians, and finally the Marsians, laid down their arms before the end of the year. Their submission was facilitated by the Lex Plautia Papiria, proposed by the Tribunes M. Plautius Silvanus and C. Papirius Carbo (B.C. 89), which completed the arrangements of the Lex Julia, and granted, in fact, every thing which the Allies had demanded before the war. All citizens of a town in alliance with Rome could obtain, by this law, the Roman franchise, provided they were at the time resident in Italy, and registered their names with the Prætor within sixty days.
The war was thus virtually brought to a conclusion within two years, but 300,000 men, the flower of Rome and Italy, perished in this short time. The only nations remaining in arms were the Samnites and Lucanians, who still maintained a guerrilla warfare in their mountains, and continued to keep possession of the strong fortress of Nola, in Campania, from which all the efforts of Sulla failed to dislodge them.
It now remained to be settled in what way the new citizens were to be incorporated in the Roman state. If they were enrolled in the thirty-five tribes, they would outnumber the old citizens. It was therefore resolved to form ten new tribes, which should consist of the new citizens exclusively; but, before these arrangements could be completed, the Civil War broke out.