The siege of Clunia (75 BC) saw Sertorius rebuild his army while being besieged by Pompey and Metellus, and then escape to join his new army (Sertorian War).
The campaign of 75 BC saw Sertorius suffer a series of setbacks. His most able subordinate, Hirtuleius, was defeated and killed by Metellus, possibly at Segovia. His less able subordinate Perpenna was defeated outside Valentia, and the city fell to Pompey. Pompey then attempted to defeat Sertorius’s main army before Metellus could arrive to share the glory, but the resulting battle of Sucro was an inconclusive clash. Both sides were ready to resume the battle on the second day, but Metellus them arrived and Sertorius decided not to risk a battle against both armies. A second inconclusive battle followed soon afterwards at Saguntum or the Turia.
In the aftermath of this second battle Sertorius decided to retreat into the mountains. He took refuge in a strong city. This isn’t identified by name by Plutarch, but the summary of Livy for this year has Sertorius besieged in Clunia, in the upper reaches of the Duero valley.
Sertorius behaved as if he was prepared to resist a siege, repairing the city walls and strengthening the gates. However his real plan was to attract Pompey’s and Metellus’s attention while his agents and allies raised a new army. Pompey and Metellus fell for the trick. They settled down to besiege Clunia, and allowed any of the Spanish who attempted to leave the city to escape. In fact most of these Spanish ‘refugees’ were actually messengers, taking Sertorius’s orders to his allied cities.
After an unspecified period of time Sertorius’s new army was ready. A message was sent to Clunia, and Sertorius was easily able to cut his way through the Roman siege lines and join up with his new forces.
After escaping from Clunia, Sertorius used his new army to ambush his enemies supplies, out march them and generally confuse them. Eventually Pompey and Metellus were forced to retreat into winter quarters, with Pompey remaining in northern Spain but Metellus retreating to Gaul. From his winter camp Metellus issued a proclamation putting a price on Sertorius’s head. Eventually Sertorius was indeed assassinated, but by one of his subordinates, Perpenna, who then attempted to continue the war.