Sulla's first civil war

Sulla's first civil war was one of a series of civil wars in ancient Rome, between Gaius Marius and Sulla, between 88 and 87 BC.

Prelude - Social War
The Social War (91–87 BC) was fought against the Socii, Roman allies in Italy, and was the result of Rome's intransigence in regarding the civil liberties of its own citizens (Romans) as superior to those of the citizens of the rest of Italy. Subjects of the Roman Republic, these Italian provincials might be called to arms in its defence or might be subjected to extraordinary taxes, but they had no say in the expenditure of these taxes or in the uses of the armies that might be raised in their territories. The Social War was, in part, caused by the assassination of Marcus Livius Drusus the Younger. His reforms were intended to grant to the Roman allies in Italy full Roman citizenship, which would have given the provincials a say in the external and internal policies of the Roman Republic. When Drusus was assassinated, most of his reforms addressing these grievances were declared invalid. This declaration greatly angered the Roman provincials, and in consequence, most allied against Rome.

At the beginning of the Social War, the Roman aristocracy and Senate began fearing Marius' ambition, which had already given him six consulships from 104 BC to 100 BC. They felt determined that he should not have overall command of the war in Italy. In this last rebellion of the Italian allies, Sulla served with brilliance as a general. He outshone both Marius and the consul Gnaeus Pompeius Strabo (the father of Pompey Magnus). For example, in 89 BC Sulla captured Aeclanum, the chief town of Hirpini, by setting the wooden breastwork on fire. As a result of his success in bringing the Social War to a successful conclusion, he was elected consul for the first time in 88 BC, with Quintus Pompeius Rufus (soon his daughter's father-in-law) as his colleague.

Sulla's Mithridatic command
As the consul of Rome, Sulla prepared to depart once more for the East to fight against King Mithridates VI of Pontus, a command that Marius (now an old man) had coveted. Marius convinced the tribune Publius Sulpicius Rufus to call an assembly and revert the Senate's decision on Sulla's command. Sulpicius also used the assemblies to eject Senators from the Roman Senate until there were not enough senators to form a quorum. Violence in the Forum ensued and the efforts of the nobles to effect a public lynching similar to that which had happened to the brothers Gracchi and Saturninus were smashed by the gladiatorial bodyguard of Sulpicius. Sulla was forced to take refuge in Marius' house, and possibly made a personal plea to stop the violence, which was ignored. Sulla's own son-in-law was killed in those riots.

Sulla's march on Rome
Sulla fled Rome and went to the camp of his victorious Social War veterans, waiting to cross to Greece from the south of Italy. He announced the measures that had been taken against him, and his soldiers stoned the envoys of the assemblies who came to announce that the command of the Mithridatic War had been transferred to Marius. Sulla then took six of his most loyal legions and marched on Rome. This action was an unprecedented event. No general before him had ever crossed the city limits, the pomoerium, with his army. It was so unethical that most of his senatorial officers (with the exception of one, probably Lucullus) refused to accompany him. Sulla justified his actions on the grounds that the Senate had been neutered and the mos maiorum ("The way things were done", or "the custom of the ancestors", which as a reference amounted to a Roman constitution although none of it was codified as such) had been offended by the negation of the rights of the consuls of the year to fight the wars of that year. A force of armed gladiators raised by the Marians (Marius offered freedom to any slave that would fight with him against Sulla) failed to resist Sulla's organized military force and Marius and his followers fled the city.

Sulla and his supporters in the Senate passed a death sentence on Marius, Sulpicius and a few other allies of Marius. A few men were executed, but (according to Plutarch) Marius narrowly escaped capture and death on several occasions and eventually found safety in Africa.

Sulla consolidated his position, declared Marius and his allies hostes (public enemies) and addressed the Senate in harsh tones, portraying himself as a victim, presumably to justify his violent entrance into the city. After restructuring the city's politics and with the Senate's power strengthened, Sulla returned to his camp and proceeded with the original plan of fighting Mithridates in Pontus (in what became the First Mithridatic War).

Aftermath
Sulpicius was betrayed and killed by one of his slaves, whom Sulla subsequently freed then executed. Marius, however, fled to safety in Africa. With Sulla out of Rome, Marius plotted his return. During his period of exile Marius became determined that he would hold a seventh consulship, as foretold by the Sybil decades earlier.

Fighting broke out between the conservative supporters of Sulla, led by Gnaeus Octavius (consul of 87), and the popularis supporters of Cinna. Marius along with his son then returned from exile in Africa with an army he had raised there and by the end of 87 BC combined with Cinna and the Roman war hero Quintus Sertorius to enter Rome, oust Octavius and take control of the city. Based on the orders of Marius, some of his soldiers (who were former slaves) went through Rome killing the leading supporters of Sulla, including Octavius. Their heads were exhibited in the Forum. After five days, Quintus Sertorius and Cinna ordered their more disciplined troops to kill Marius's rampaging slave army. All told some 12 Roman nobles had been murdered.

Marius declared Sulla's reforms and laws invalid, officially exiled Sulla and had himself elected to Sulla's eastern command and himself and Cinna elected consuls for the year 86 BC. Marius died a fortnight after and Cinna was left in sole control of Rome. Sulla's second civil war would soon result.