The siege of Lacobriga (78 BC) saw Sertorius outwit Metellus and foil his attempt to capture the chief city of one of Sertorius’s Spanish allies.
Lacobriga was one of the chief cities of the Lusitanians, the group who had originally invited Sertorius back into Spain at the start of the Sertorian War. They were also the main threat to Metellus Pius’s province of Further Spain, and the inhabitants of Lacobriga had given significant assistance to Sertorius.
Metellus decided that the city of Lacobriga (modern Lagos in southern Portugal) was vulnerable to attack, as there was only one well within the city walls and the rest of the city’s water came from streams in the suburbs that would be denied to them in a siege. He expected that the siege would only last two days, due to the lack of water, and so he ordered his men to only bring supplies for five days.
Sertorius must have been in the area, as he responded quickly. He ordered 2,000 water skins to be filled, offering to pay well for them. He then selected an elite force that he used to carry the water into the city, using a route that passed through the mountains (presumably to the west of the city). The same men then evacuated the bulk of the population, leaving only the defenders behind.
Metellus was now in a difficult position, as his men had already used up their supplies. He sent out 6,000 men under Aquinus to forage more supplies, but Sertorius ambushed the foraging party. He hid three thousand men in a ravine close to Aquinus’s return route. As Metellus’s men returned to the siege lines, Aquinus attacked from the rear and Sertorius from the front, routing Aquinus who was forced to abandon his armour and his horse.
After this setback Metellus abandoned the siege and retreated east into the safer part of his province.