The Crossing the Rubicon was the opening act of Caesar's Civil War, occurring on 10 January 49 BC when Julius Caesar and his Legio XIII Gemina crossed the Rubicon River, thus marching from Cisalpine Gaul southwards into the province of Italia, in violation of a Roman law forbidding generalsl from leading their armies into the latter province. Caesar's crossing was unopposed, and, while Pompey had three legions in arms to defend the city, most of the men were raw recruits, and the rest were veterans of the Gallic Wars and were loyal to Caesar. Pompey opted to make a tactical retreat to Corfinium, where he would gather his legions to retake Rome, but Caesar quickly occupied northern and central Italy and forced Pompey to flee to Greece.
Background[]
By 52 BC, Julius Caesar was still Governor of Gaul, and had applied to run for the consulship in absentia in 48 BC, as his term as governor would end in 49 BC. As, that year, Rome was in a chaotic state due to riots and violence between Publius Clodius Pulcher's Populares and Titus Annius Milo's Optimates, Caesar's application was allowed with little thought. However, Caesar's enemies were concerned that Caesar would easily win the consulship due to his vast popularity, and they also grew concerned that a continued political career would ensure that Caesar would continue to hold legal immunity.
Moreover, Caesar would be able to use his consulship to push legislation to protect himself. His enemies in the Roman Senate accused him of stirring political violence against a fellow consul and instigating wars in Gaul and Britain without senatorial approval. Conservative statesman Cato the Younger made it clear that, given the opportunity, he would put Caesar on trial himself, should Caesar become a private citizen. Cato ran for the consulship in 51 BC, hoping to use consular power to deprive Caesar of his command, but he failed, and, over the next two years, Cato led the Senate in demanding Caesar's resignation. However, the tribunes Mark Antony and Gaius Scribonius Curio, who were loyal to Caesar, blocked and vetoed such legislation. The Senate insisted that Caesar's term ended in 50 BC and ordered him to relinquish his command, but Caesar refused, knowing that the Senate would put him on trial should he resign, and that his term did not expire until the end of 49 BC.
In December of 50 BC, Caesar's former ally and the military leader of the Optimates, Pompey the Great, offered to resign his command if Caesar would first, but the Caesarians demanded that Pompey resign first. Neither side was willing to be exposed, and, that same month, Caesar marched to Ravenna with Legio XIII Gemina to winter there, and he sent letters to Pompey offering to resign his command if Pompey would first. However, rumors soon spread that Caesar had four legions with him instead of one, and the Senate believed that Caesar was attempting to threaten and blackmail him. They ordered Caesar to stand down immediately and had Pompey raise legions in defense of Rome, but Caesar instead offered to resign his governorships in Gaul and command over most of his legions, in exchange for serving as Governor of Illyria and maintaining command of two legions, and being able to run for consul in 48 BC. The conciliatory Marcus Tullius Cicero negotiated Caesar down to just one legion and one province, and, while Pompey agreed, the Optimates Cato and the consul Lucius Cornelius Lentulus Crus steadfastly opposed dealing with Caesar, hating the idea of the Senate being pressured to negotiate.
On 7 January 49 BC, the Senate voted to strip Caesar of his powers and armies, but Curio and Antony vetoed the legislation. In response, the Senate passed an un-vetoable act which suspended all laws and granted all powers to the consuls, and declaring Caesar an enemy of the state. The consuls passed all of their powers to Pompey, giving him full control of the Roman Republic, and leading to Caesar's allies in Rome fleeing to Ravenna to join him. The division between the Populares (younger men from less-established families, and lesser members of noble families) and Optimates (aristocrats of noble families) was thus finalized, and the societal rift plunged the Republic into chaos once again.
History[]
On 10 January 49 BC, Caesar left Ravenna with Legio XIII Gemina and his allies from Rome, and they halted at the small Rubicon River, which marked the border of Cisalpine Gaul and Italia, into which no Roman general could cross with arms or an army. Caesar hesitated before crossing the river, as he was aware of the mass destruction of a civil war, but was also aware that resigning command of his armies would mean exile or execution. After almost a day's deliberation, Caesar decided, "The die is cast," and he crossed the river with his legion, initiating the civil war.
Map of Caesar's advance on Rome
Following the crossing, Caesar moved with swiftness and quickly seized key locations in northern Italy with little resistance. These cities were not garrisoned to defend against any significant force, and many sympathized with Caesar against Pompey and the Optimates. Caesar sent for his Gallic legions to march south and join him. In Rome, Pompey mistakenly believed that Caesar would wait for his legions from Gaul before attacking Rome, and he, too, hesitated. While Pompey could have levied enough troops from Italy to fight Caesar had he stayed in Rome, Pompey was unaware that Caesar had just one under-strength legion under his command. Pompey's Legio I could be trusted to fight on his behalf, but his Legio XV was raised by Caesar and had questionable loyalties; most of Pompey's best legions were abroad either in Hispania or the Levant. Pompey could afford to fight a prolonged war with the resources of the Republic at his disposal, so he made the difficult decision to abandon Rome, and the majority of the Senate and both consuls accompanied Pompey in leaving Rome; in the rush to evacuate the city, the treasury of Rome and the temple treasures were abandoned. Caesar decided to bypass Rome and catch Pompey, capturing other cities in Italy to cut off support from the Pompeians and rally reinforcements for his cause. However, while most of Caesar's allies in Rome had joined him, his former second-in-command in Gaul Titus Labienus, refused to march his Gallic legions to Italy and join the fight there, disavowing Caesar and taking his personal bodyguard with him to join Pompey. Caesar's legions still followed their orders to move towards Italy, with Legio VIII and Legio XII marching into Italy to support their general.