In 88 BC, Lucius Cornelius Sulla marched his legions on Rome, starting a period of civil wars.
[4] Unfortunately his faction lost the war in Italy right after his departure, and in 81 BC Sulla sent Gaius Annius Luscus with several legions to take the Iberian provinces from Sertorius.
In 80 BC Sertorius landed at the little fishing town of Baelo near the Pillars of Hercules (Gibraltar) and returned to Hispania.
Threatened by Sertorius' successes, the Senate in Rome upgraded Hispania Ulterior to a proconsular province and sent the proconsul Quintus Caecilius Metellus Pius with a large army to fight him.
[9] In 75 BC Sertorius decided to take on Metellus and leave the battered Pompey to his legates Perpenna and Gaius Herennius.
Metellus used the change in command to defeat Hirtuleius, left in charge of the Sertorian western army, at the Battle of Italica and marched after Sertorius.
With his forces morale raised he awaited the Roman armies while launching many guerilla raids to weaken them during their advance.
The Romans were hard pressed for supplies and Metellus decided to march on the Celtiberian town of Segontia to feed his army on their stores.
After Hirtuleius had fallen Sertorius switched places with Perpenna and launched several attacks on Metellus intended on taking him out of the fight.
Sertorius in the meantime had regrouped his men and in the evening launched an unexpected attack on Metellus' camp, and attempted to exploit its vulnerable position by cutting it off with a trench.
After the Siege of Clunia he reverted to guerilla warfare and the war would drag on for another three years and only end because a few of his own men plotted against Sertorius and assassinated him.