After pretending to be ready to negotiate with some of his neighbors, Mehmed II besieged Sinope and obtained its surrender. The Sultan sent his fleet on to Trebizond, while he led the land army against Uzun Hassan. After Mehmed took the frontier fortress of Koylu Hisar by storm, and Uzun Hassan's allies the Karamanians failed to come to his aid, Uzun Hassan sent his mother, Sara Khatun, with expensive gifts to the Sultan's camp to sue for peace. While she managed to negotiate a peace treaty between Mehmed and the Aq Qoyunlu, she could do nothing for her daughter-in-law's homeland, Trebizond. Steven Runciman repeated the exchange between Sara and Mehmed: "Why tire yourself, my son, for nothing better than Trebizond?" she asked him. He replied that the Sword of Islam was in his hand, and he would be ashamed not to tire himself for his faith.