Sertorius was born around 123 BC in Nussa, a city of the Sabines. He is first noted as campaining with the proconsul Quintus Servilius Caepio at the battle of Arausio in 105 BC. Even in his first battle, he showed incredible courage and soon became famous because of this. He then served under Gaius Marius and proved his worth time and time again. Even tough he gained positions of command, he never stopped being a soldier by heart. He was always in the thick of battle for which he also lost one of his eyes. Even tough his was no close ally of Marius, he sided with the Populares during Sulla's civil wars. After the defeat of the Populares at the hands of the Optimates, he had to flee Rome with a small army and the majority of the populares remaining, to Hispania in 83 BC.
Sulla would not be satisfied with this, and after sending an army after him and a betrayal from his own subordinates, Sertorius was forced to sail to Mauretania. There Sertorius conducted great military campaings in the country's civil war, after which his fame became even greater. Even tough he conquered Tingis, and had control over the entire country, he did not seek to assert himself as the leader of the state and returned the power to the rightfull ruler. Admired for this, Sertorius receved many gifts from the local noblemen, becoming a very rich man.
In 80 BC a Lusotanian embassy was sent to Mauretania. The Lusotanians, a proud and fighting people, resented the Roman treatment of them while they were under the SPQR and their fightng spirit was as eager as ever. All they needed was a great general, that could lead them to great things, like Viriathus did before that. They found that general in Sertorius.
Later that year Sertorius sailed again for Hispania. He had only a small army with him, comprimising of troops from Rome, Iberia and Africa, but his forces would soon expand. In the homeland of the Lusotanians he was given all the powers that he could wish for, acting as the high-king of the western tribes of Iberia. That same year, Sertorius and his quaestor Hirtuleius defeated two Roman armies, led by the governors of the two Hispanias, Ulterior and Citerior. Many tribes and cities joined the Sertoriani cause, and even tough Mettelus Pius, the consul, was sent to Hispania, he couldn't stop what Sertorius began. At the hight of the Sertoriani power, almost all of Hispania, except the far south and north, was under the control of the populares. Mighty cites like Tarraco, Valentia, Osca and Carthago Nova were siding with this never defeated general. The situation in Rome became dire. In 77 BC the young Pompey Magnus was sent to Hispania with a great army to stop the rebellion. But the same year, after the defeat of Lepidus in Italy, Marcus Perperna Vento joined Sertorius with large forces, and once again the power of the rebels increased. Pompey and Metellus were defeated many times. Sometimes in open battle, sometimes with timely ambushes. For Sertorius often used this tactic, which came so natural to the Iberian peoples, and with it he had great success. We have numerous reports of Sertorius wiping out more then a 1.000 soldiers of the enemy with well prepared ambushes, with barely any losses to his troops. The sitaution became so dire, that Pompey threatened that he would march on Rome, if he would not receive a large amount of soldiers and money to try and defeat Sertorius. It is obvious, since Lucullus agreed to give Pompey what he needed, that Pompey actually had the strenght to conquer Rome, but not the strenght to defeat Sertorius. And that's a statement that makes one think.
The capital of this new state was Osca. There Sertorius found a new senate of 300 Roman exiled senators, and also built a school, where the children of the elite of the Hispanian tribes would be edjucated in a Roman way. Osca also minted it's own coins. These were the foundations of a new state, that would exist beside the Roman one, if the Optimates would remain in power in the City.
Sertorius held his own in Hispania until 72 BC, where he was assasinated by his second in command, the before mentioned Marcus Perpenna Vento. He tried then to lead the young state on his own accord, but seeing their leader dead, the Iberians started to desert the cause that Sertorisu put in place, and Vento was utterly defeated in his first battle against Pompey. Thus Pompey became the re-conqueror of Hispania, something he couldn't do, while Sertorius was still alive, even tough he had all the resources of the Republic at his disposal.