In 1185 Saladin was campaigning against Izz ad-Din Mas'ud, the Zengid ruler of Mosul. At this time Gökböri came under suspicion of collusion with Izz ad-DIn. Gökböri had promised the sultan a large sum of money towards the cost of the campaign, but was unable to produce it. Saladin had Gökböri arrested, but quickly released him. Saladin became gravely ill during this campaign, but was nursed back to health in Gökböri's castle at Harran. In 1186 the war ended, when Izz ad-Din Mas'ud agreed to become Saladin's vassal.Runciman, pp. 445-446Ehrenkreutz, p. 189
