In the Battle of Alesia in September 52 BC, Caesar built a fortification around the city to besiege it. However, Vercingetorix had summoned his Gallic allies to attack the besieging Romans. These forces included an army of Arverni led by Vercingetorix's cousin Vercassivellaunos and an army of 10,000 Lemovices led by Sedullos.