His early years
As Julius Caesar aged into his early teenage years, the political climate of Rome was in turmoil. By 88 BC, the rivalry between Gaius Marius and Lucius Cornelius Sulla was heating into open civil war. Attempts by Marius supporters to overturn Sulla's command against Mithridates VI of Pontus, prompted Sulla's subsequent march on Rome. Sulla took control of the city by force, and many of Marius' supporters were put to the sword. Caesar, despite his relation to Marius, was still a boy and for the time being, was excused from any potential danger.
Soon after, Sulla marched east to fight the first Mithridatic War. With his legions away from the capital, Marius, and a deposed Consul, Lucius Cornelius Cinna, gathered strength and made their own march on Rome. By 86 BC, both men were elected Consul, and in retribution, a bloodbath against Sulla's supporters took place. These events, along with the history of Rome in Caesar's near past must've been key factors on the young man's development. From the time of his birth through his early formative years, all Rome seemed to know was political uncertainty, violence, and the uncertainty of what was to come. From the social disorder brought on by the Gracchi 30 years before his birth to the deep involvement of his own family in various situations, Caesar's view on Roman politics would surely be a major impact later. In light of the status quo of continuous factional fighting, as opposed to the potential stability and control of a single powerful ruler, these events in Caesar's life were a powerful force.
Marius died shortly after election to his record Consulship. While the relationship between the young Caesar and Marius on a personal level is largely unknown, there is little question of his relationship to his aunt Julia, Marius' wife. As evidenced by a later funeral oration of her, she was an influential force to him, and it stands to reason that the uncle was as well. Regardless, he certainly fell under the indirect influence of the surviving Consul Cinna. He ruled Rome after the death of Marius, and in the absence of Sulla, with an iron-handed will for the next few years. During this time, Caesar was appointed to the office of Flamen Dialis, or head priest of Jupiter, by Cinna. This priesthood was filled with many strict rules based on the lore and rituals of the ancient religion. The flamen dialis could never touch metal, see a corpse, ride a horse, and was restricted in many foods, among many other things. It seems likely that, possibly due to his youth, he was never actually confirmed in this role, in light of his future career as both a politician and a soldier. Whatever the reason, it's evident that he held the position only a short time, and the ancient sources make little mention of his dismissal as a priest.
Shortly after his appointment as flamen, Caesar's association with the populares political party was cemented further by marriage. In 84 BC, he was married to Cinna's daughter Cornelia, which would have lasting ramifications. Just a year later, as Cinna prepared to meet Sulla's victorious legions as they returned to Rome, his own troops mutinied and Cinna was killed. Sulla marched into Italy and within a year defeated nearly all opposition. In 81 BC, after the battle of the Colline Gate, Sulla was the undisputed victor, and soon assumed the title of dictator. Sulla's victory was to be another profound event in the life of Caesar. Not only was he a member of the opposition party, by virtue of his family and marriage, but Sulla's behavior also helped shaped Caesar's later leniency toward opposition.
With Sulla in charge of Rome, a political and brutally bloody purge of his enemies commenced. In a term labeled as proscription, in which enemies were publicly listed for execution and/or confiscation of properties, Sulla began the systematic reversal of all opposition to his pro Senatorial elite, or optimate, agenda. Caesar certainly was named on the proscription lists, and at the age of 19, he left his young wife and family to avoid the death penalty. Disguised and assumedly with the help of substantial bribes, he escaped Rome and went into hiding in the Italian countryside.
Caesar's family, and likely with great influence from his mother Aurelia, along with the College of Vestal Virgins, as he was still technically the flamen dialis, worked hard on reversing Sulla's proscription. Eventually Sulla rescinded the sentence of death for Caesar, and he was free to return to Rome. Sulla instead demanded that Caesar divorce the daughter of his former rival Cinna, but Caesar refused. Amidst the pressure from Caesar's family Sulla still pardoned him, confiscating Cornelia's dowry instead. In a prophetic moment, Sulla was said to comment on the dangers of letting Caesar live. According to Suetonius, the dictator in relenting on Caesar's proscription said, "Take him then, my masters, since you must have it so; but know this, that he whose life you so much desire will one day be the overthrow of the part of nobles, whose cause you have sustained with me; for in this one Caesar, you will find many a Marius."