Lucius Licinius Lucullus was a new man (novus homo) who became consul in 151 BC. This was a term for men with plebeian background who attained the consulship and had no ancestors who served as consuls (originally the consulship was monopolised by the patrician aristocracy).
Lucullus was sent to Hispania Citerior (Nearer Spain, on the east coast of Hispania) when the senate rejected a proposal for a peace treaty with the Celtiberians by Marcus Claudius Marcellus to end the Numantine War (154–152 BC). However, Marcellus went ahead with his plan and quickly concluded a treaty before Lucullus got there. Lucullus was disappointed and, "being greedy of fame and needing money because he was in straitened circumstances", he attacked the Vaccaei (a Celtiberian tribe which lived further north) who were not at war with Rome and did so without the authorisation of the senate. He claimed that they had mistreated the Carpetani as an excuse.
He pitched camp by the town of Cauca (near modern Segovia) and when its people asked for peace terms he demanded, among other things, that a garrison be placed in the town. He got his soldiers to kill all the adult males. Only a few out of 20,000 escaped. Lucullus then went the city of Intercatia (Villanueva del Campo, in the modern province of Zamora) whose inhabitants, having heard about Cauca, refused to ask for terms. He struggled to seize the city, and his lieutenant, Scipio Africanus the Younger, promised the Inercatians that if they made a treaty it would not be broken. They trusted him and surrendered. Luculllus was advised not to attack the large city of Pallantia (modern Palencia), which hosted many refugees and was renowned for its bravery, but because he heard that it was a rich city he camped there. The Pallantians cavalry constantly harassed his foragers until he ran out of food and he had to withdraw. He set up winter camp in the land of the Turdetani (in modern Andalusia).