Thus, there is an unresolved question about the end of the Roman Republic: when a new politician and general named Julius Caesar became increasingly powerful and ultimately began to replace the Republic with an empire, was he merely making good on the threat posed by Marius and Sulla, or was there truly something unprecedented about his actions? Julius Caesar’s rise to power is a complex story that reveals just how murky Roman politics were by the time he became an important political player in about 70 BCE. Caesar himself was both a brilliant general and a shrewd politician; he was skilled at keeping up the appearance of loyalty to Rome's ancient institutions while exploiting opportunities to advance and enrich himself and his family. He was loyal, in fact, to almost no one, even old friends who had supported him, and he also cynically used the support of the poor for his own gain.
Two powerful politicians, Pompey and Crassus (both of whom had risen to prominence as supporters of Sulla), joined together to crush the slave revolt of Spartacus in 70 BCE and were elected consuls because of their success. Pompey was one of the greatest Roman generals, and he soon left to eliminate piracy from the Mediterranean, to conquer the Jewish kingdom of Judea, and to crush an ongoing revolt in Anatolia. He returned in 67 BCE and asked the senate to approve land grants to his loyal soldiers for their service, a request that the senate refused because it feared his power and influence with so many soldiers who were loyal to him instead of the Republic. Pompey reacted by forming an alliance with Crassus and with Julius Caesar, who was a member of an ancient patrician family. This group of three is known in history as the First Triumvirate.
Each member of the Triumvirate wanted something specific: Caesar hungered for glory and wealth and hoped to be appointed to lead Roman armies against the Celts in Western Europe, Crassus wanted to lead armies against Parthia (i.e. the “new” Persian Empire that had long since overthrown Seleucid rule in Persia itself), and Pompey wanted the senate to authorize land and wealth for his troops. The three of them had so many clients and wielded so much political power that they were able to ratify all of Pompey's demands, and both Caesar and Crassus received the military commissions they hoped for. Caesar was appointed general of the territory of Gaul (present-day France and Belgium) and he set off to fight an infamous Celtic king named Vercingetorix.
From 58 to 50 BCE, Caesar waged a brutal war against the Celts of Gaul. He was both a merciless combatant, who slaughtered whole villages and enslaved hundreds of thousands of Celts (killing or enslaving over a million people in the end), and a gifted writer who wrote his own accounts of his wars in excellent Latin prose. His wars were so far-ranging that he even invaded England, establishing a Roman territory there that lasted centuries. All of the lands he invaded were so thoroughly conquered that the descendants of the Celts ended up speaking languages based on Latin, like French, rather than their native Celtic dialects.
Caesar's victories made him famous and immensely powerful, and they ensured the loyalty of his battle-hardened troops. In Rome, senators feared his power and called on Caesar's former ally Pompey to bring him to heel (Crassus had already died in his ill-considered campaign against the Parthians; his head was used as a prop in a Greek play staged by the Parthian king). Pompey, fearing his former ally’s power, agreed and brought his armies to Rome. The senate then recalled Caesar after refusing to renew his governorship of Gaul and his military command, or allowing him to run for consul in absentia.
The senate hoped to use the fact that Caesar had violated the letter of Republican law while on campaign to strip him of his authority. Caesar had committed illegal acts, including waging war without authorization from the senate, but he was protected from prosecution so long as held an authorized military command; by refusing to renew his command or allow him to run for office as consul, he would be open to charges. His enemies in the senate feared his tremendous influence with the people of Rome, so the conflict was as much about factional infighting among the senators as fear of Caesar imposing some kind of tyranny.
Caesar knew what awaited him in Rome - charges of sedition against the Republic - so he simply took his army with him and marched off to Rome. In 49 BCE, he dared to cross the Rubicon River in northern Italy, the legal boundary over which no Roman general was allowed to bring his troops; he reputedly announced that “the die is cast” and that he and his men were now committed to either seizing power or facing total defeat. The brilliance of Caesar's move was that he could pose as the champion of his loyal troops as well as that of the common people of Rome, whom he promised to aid against the corrupt and arrogant senate; he never claimed to be acting for himself, but instead to protect his and his men’s legal rights and to resist the corruption of the senate.
Pompey had been the most powerful man in Rome, both a brilliant general and a gifted politician, but he did not anticipate Caesar’s boldness. Caesar surprised him by marching straight for Rome; Pompey only had two legions, both of whom had served under Caesar in the past. Thus, he had to recruit new troops, many of whom defected to Caesar as he marched through Italy. Pompey fled to Greece, but Caesar followed him and defeated his forces in battle in 48 BCE. Pompey himself escaped to Egypt, where he was promptly murdered by agents of the Ptolemaic court who had read the proverbial writing on the wall and knew that Caesar was the new power to contend with in Rome. Caesar himself came to Egypt and stayed long enough to forge a political alliance, and carry on an affair, with the queen of Egypt: Cleopatra VII, last of the Ptolemaic dynasty. Caesar helped her defeat her brother (to whom she was married, in the Egyptian tradition) in a civil war and to seize complete control over the Egyptian state. She also bore him his only son, Caesarion.
Caesar returned to Rome two years later after hunting down Pompey's remaining loyalists. There, he had himself declared dictator for life and set about creating a new version of the Republic that answered directly to him. He filled the senate with his supporters and established military colonies in the lands he had conquered as rewards for his loyal troops (which doubled as guarantors of Roman power in those lands, since veterans and their families would now live there permanently). He established a new calendar, which included the month of “July” named after him, and regularized Roman currency. Then he promptly set about making plans to launch a massive invasion of Persia.
Instead of leading another glorious military campaign, however, in March of 44 BCE Caesar was assassinated by a group of senators who resented his power and genuinely desired to save the Republic. The result was not the restoration of the Republic, however, just a new chapter in the Caesarian dictatorship. Its architect was Caesar’s heir, his grand-nephew Octavian, to whom Caesar left (much to almost everyone’s shock) almost all of his vast wealth.