After the death of Silla, power theoretically returned to the Senate. Still, the Senate itself leaned on two lieutenants of Silla, the most potent individuals now in Rome: Pompey and Crassus.

From a wealthy family, Marcus Licinius Crassus had become even richer with the confiscations during the times of Silla, and this wealth allowed him to play a major political role. In 73, slaves at a gladiator school in Capua revolted; they were gladiators, therefore they were well trained and prepared. They were led by a slave from Thrace, Spartacus, who knew the Roman military tactics because he had fought in the Roman army. The revolt started with a small group of skilled fighters, but it quickly spread to large areas of southern Italy; it was a clear sign of the desperation of thousands of slaves; and surprisingly, they were joined by many peasants and small farmers, for many Roman citizens the living conditions were so poor that they chose to join the slaves in the revolt.

To fight this war, which was called "the slave war", the Senate gave Crassus the command of 8 legions, some of which he probably financed himself. After a great battle in Apulia in which Spartacus died, in 71, the war was over: Crassus had 6.000 prisoners crucified along the Appian Way.

The other protagonist of these years is Pompey: after being a supporter of Silla, in 76, he was sent to Spain to fight the Roman governor Sertorius, who ruled his provinces as an independent king. After taming the revolt, he returned and signed a pact with Crassus: both would be consuls in the following year. And so it happened. But it was Pompey that the Senate appointed as leader of a great army to fight pirates in the western Mediterranean.

With extraordinary powers and an army of 120,000 soldiers and 500 ships, Pompeius got rid of the pirates and cleared the sea routes in a few weeks. Then he was ordered to turn against King Mithridates of Ponto (now Armenia), but he went far beyond his mandate: he defeated King Mithridates, subdued Armenia, annexed Syria, and intervened between the two heir brothers to the throne of Judea, and made it a tributary state.

Now the Eastern Mediterranean was controlled, directly or indirectly, by Rome. Pompeius acted without even caring to be authorised by the Senate; he acted on his own initiative, as a monarch: he deposed kings, created others, set territories as Roman provinces, allowed others to remain independent under Rome’s control, which was also a way for him to obtain the future support of these kings. This meant that the Senate, which traditionally had the responsibility of foreign policy, was losing power, and it set a precedent that other generals would follow.

At this point, it was evident that in Rome’s policy, conquest and exploitation prevailed over anything else. Rome no longer needed to justify its aggressive policy since there was no public opinion of any kind anymore; it was the most powerful state in the Mediterranean and thus had the right to dominate all other peoples and establish a universal empire.

Pompey was now immensely rich; he dissolved the army as he was legally compelled to do and returned to Rome in 62. He thought that his popularity and influence were so great as to guarantee him the undisputed supremacy of the state. But he was wrong: now that he did not have an army to back him, senators thought he was not so dangerous, after all. The decisions he had taken in the East were not validated, and his veterans were not even granted the lands he had promised them. This led him to turn against the Senate and look for the help of an old friend, Crassus, and through him of Marius' nephew, who was now the leader of the populares: Julius Caesar.

Caius Julius Caesar came from a poor aristocratic family that traced its origins to King Ancus Martius and the goddess Venus. He was probably born in 100 B.C. He was Marius' nephew, and his family ties put him among the populares. Caesar was a perfect man of the times, elegant, unscrupulous and full of humour.

At that time, the contrast between the senatorial and the popular factions was very violent, and in 74, Caesar left for Cilicia to escape his enemies. A pirate boat captured him at sea, and the pirates demanded 20 talents for his ransom. Caesar replied insolently that it was too low a price for his value, and he preferred to give them 50. He sent his servants to get them; while in prison, he wrote verses and red them to the pirates but also promised to hang them. Which he did because, as soon as he was freed, he ran to Miletus, rented some boats, chased the pirates and captured them, took his money back and had them all slaughtered.

Caesar belonged to an ancient family and its relationships, together with some good marriages and the massive number of votes he literally bought, and he spent a lot of money for them; they secured him a series of important public offices. Finally, in 69, he was appointed Governor of Spain. Here he subdued the area's peoples and brought back to Rome a loot so big that the Senate granted him the triumph.

Back in Rome, Caesar proposed to Crassus and Pompey to forge a three-party private partnership that historians will call “the first triumvirate". Each of the three would manoeuvre the masses of followers at his disposal and pass laws to benefit the other two. Caesar was the least important and influential of the three men, and therefore he benefited most from this pact.

With the support of his new allies, he was elected consul for the year 59. Immediately, he had Pompey’ decisions in the East ratified and lands distributed to Pompey’ veterans. Then, to consolidate the alliance, he gave Pompey his daughter Giulia as a wife. He then appointed himself proconsul (governor) of the provinces of Gallia, for five years, never happened before: thus, he could undertake a lengthy military campaign without having to give up command. His conquest would make him as popular as Pompey and provide his soldiers with enrichment opportunities.

The Gauls belonged to the great family of Celtic peoples and were divided into about 50 tribes. They lived in large villages; their economy was based on agriculture, cattle breeding, iron and metalworking. The various tribes were constantly at war with each other. In Caesar's time, Roman merchants travelled extensively across the region: it was often they who provided the general with directions and news. Caesar focused on these divisions; he only had four legions for all that territory, not even 30,000 men. And just as he took over, 400,000 Helvetii were heading for Gallia Narbonensis, southern  France, from Switzerland, and 150,000 Germans had crossed the Rhine to invade Flanders.

Several Gallic tribes asked for Rome’s protection and Caesar, without even notifying the Senate, enlisted another four legions at his own expense. The two campaigns were dazzling. He beat the Helvetii so hard, despite their enormous superiority, that they asked for permission to withdraw to their homeland, and Caesar allowed it, as long as they accepted to be subjects of Rome. Even the Germans were annihilated in a battle. Now, the underestimated women chaser turned out to be a formidable general on the battlefield, with an intuitive tactical genius but also with absolute contempt for human life.

Caesar's conquests in Gaul made him equal to his associates, both for his military reputation and financial resources. In the dispatches he sent home, Caesar thrilled his fellow citizens with reports of the Rhine crossing in the campaign against the Germans and the exploration of Britannia, Britain, these acts had little strategic value, but their purpose was to increase his legend.

In 56, Caesar met once again with Crassus and Pompey in Lucca. The three decided that Caesar's proconsulate would be renewed for another five years, while Crassus and Pompey would be Consuls in 55. After the consulate, Crassus would have the government of Syria, and from here he could earn that military glory that he lacked, unlike Pompey and Caesar; and Pompey would obtain the government of the two provinces of Spain with the command of some legions; thus he would have his own army again.

The three political leaders now had absolute power. But it was evident that sooner or later, the power struggle would blaze again, and in 54, the agreement began to weaken. The strength of the Triumvirate laid in the fact that neither of its members could stand against the other two. But the precarious balance was broken when Crassus' army was annihilated by the Parthians at Carre, in Asia Minor, nowadays Turkey, in 53: Crassus was killed, and his head was exhibited in a court play. Now Crassus could not be a counterweight anymore, in case Caesar and Pompeius quarrelled.

Back in Gaul, Caesar had a wooden bridge built in 10 days on the Rhine to show the Germans the power of Rome; he made a foray into the Germanic territory and, after returning to the left bank of the river, had the bridge destroyed. In 55 and then in 54, he landed in Britain and advanced to the Thames: never had a Roman army gone so far north.

In Rome and Italy, Caesar's fame was immense. But, in 52, a general uprising united all peoples of Gaul against the Roman occupation, under the command of a young nobleman, Vercingetorix. Vercingetorix stood with his forces between Caesar in the south and his army in the north. With a few soldiers, Caesar crossed the Alps and marched north in an enemy country. He walked day and night, in the snow, and finally managed to reach his troops.

He was alone, one against 10, in a hostile country. He decided to play it all, marching on Alesia, the city where Vercingetorix had amassed his army and besieged it. From all parts of Gallia, the Gauls rushed to free their captain. 250,000 Gauls against 4 Roman legions. Caesar ordered his soldiers to raise two lines of defence, the “valli”, one towards the besieged city and one outwards, facing the incoming forces, and among them he put his soldiers with the few ammunition and food supplies they still had.

After a week of desperate resistance on two fronts, the Romans were starving, but the Gauls were in anarchy, and they began to retreat tribe by tribe. Vercingetorix himself came out of the exhausted city to ask for grace. Caesar granted it to the city, but the rebels became the property of the legionnaires, who sold them as slaves. The unfortunate captain was taken to Rome, and the following year he followed Caesar's chariot in chains during his triumph. With one million dead and another million enslaved, Gaul became a Roman province: the region quickly turned Roman, and Roman citizenship was granted only 100 years later, under Emperor Claudius.

Now, the enemies of Caesar in the Senate opposed to his ambition to return to Rome. With the resources of Gaul at his disposal, he planned to get consulship again for the year 48. But he had to get it “In absentia”, that is, without showing up in Rome. Coming back to Rome before being nominated as consul was too dangerous, without the immunity granted by his current command in Gaul and especially by the protection of his legions, he could be prosecuted and even eliminated.

Now, his adversaries turned to Pompey; they tried to convince him that Caesar was not his ally but his rival. Due to the clashes between rival gangs, it was impossible to elect the Consuls for 54 and much of 53. Followers of the populares even set the Senate on fire. To restore order, in 52, the Senate had Pompey nominated “only” Consul and granted him the office of proconsul (governor) in Spain for five years. Now that even the Senate had resolved to invoke Pompey’s help, there was only one obstacle between him and absolute power: Caesar and his legions.

It was a dead-end, and the general feeling was that civil war was about to break out. Pompey proposed a law according to which anyone competing for consulship should be in the city and had the Assembly site surrounded by his troops. Needless to say, the general assembly approved. Thus, Caesar should go to Rome as a private citizen, far from his army. This would make him completely helpless, whereas Pompey, on the pretext of maintaining public order, kept troops in Italy and near Rome itself.

Under pressure from Pompey, the Senate officially ordered Caesar to dismiss his army by March 1^st; otherwise he would be declared a traitor. For Caesar, as he had always shown, attack was always the best defence. He had eight legions in Gaul but only one stationed in Ravenna, and it could provide only 5000 men. However, Caesar knew that, because of the political divisions within Roman society, he was a hero for the populars and would be hailed everywhere in Italy as the people's champion. Caesar spoke to his legionnaires, he called them not “milites” (soldiers) but “commilitones” (comrades) and asked if they felt like fighting against Rome, their homeland: if they lost, they would be called “traitors”. And they answered yes, unanimously.

On January 11^th, Caesar ordered the legion to march from Ravenna and camp on the north bank of the Rubicon River, which marked the border between Gaul and Italy. Arriving at the Rubicon, he stopped on the shore. The river itself did not represent a physical obstacle, still, it was a tremendous psychological barrier: it marked the border of Italy, where leading an army was unlawful, Silla had stated it. By crossing it, Caesar would no longer be a servant of the Republic but an enemy.

Around midnight of January 12^th, 49 B.C., he made his decision: with the famous motto "Alea iacta est - The die is cast" he crossed the river, starting the civil war. Even though the Republic was formally still alive, its fate was set: whoever won this war would have abolished it.