The next year Lucullus invaded Pontus. Here he finally allowed the Fimbrians to plunder and pillage. Mithridates' army disintegrated after the Battle of Cabira, whereupon the Pontic king fled east to the court of his son-in-law king Tigranes II of Armenia. When negotiations with Tigranes failed, Lucullus invaded Armenia and won victories at Tigranocerta and Artaxata. Unable to beat Lucullus in open battle, Tigranes and Mithridates began resorting to hit-and-run tactics. Winter forced Lucullus to march westward at the end of 68 BC. After 18 years of service and 960 miles (1,500 km) of marching in the last five years, the Fimbrians refused to accompany Lucullus when he marched to besiege Nisibis in northern Mesopotamia. They stayed on garrison duty in Pontus, where they were caught off guard by Mithridates when he suddenly returned to his kingdom in 67 BC at the head of a combined Armenian-Pontic army. It is unclear whether the Fimbrians fought at the disastrous Battle of Zela that year, but their continued existence as two legions in 66 BC suggests that they probably did not.