The fortress of Kemah, Idris-i Bidlisi tells us, marked the border of Rum with Iran. "He who possesses Kemah, holds the key to the world," observes Ada'i, a contemporary of Bidlisi. As such, Kemah was long fought over by Anatolian states against powers based in Iran and Iraq (such as Byzantium with the Sasanids, and later, the Umayyads and Abbasids). Kemah likewise was a main bone of contention between Timur and Bayezid I when the latter seized it from its local lord in 1401, and set off the war between the "padishahs of Iran and Turan," as Bidlisi puts it. Selim I (1512-1520) 's incorporation of the northeastern provinces on the Ottoman-Safavid frontier after the Ottoman victory at Çaldiran in 1514 necessitated possession of Kemah. Possession of Kemah was not only the key to securing Erzincan and the road to Trabzon; situated on the bank of the upper Euphrates at a distance of a day's travel from Erzincan to the east, Kemah controlled passage from Anatolia to Iran and Mesopotamia along one of the most traveled caravan routes. This paper examines both the strategical and ideological significance of Kemah, primarily drawing from contemporary Ottoman sources. Of particular importance is Idris Bidlisi's Persian Salim Shahname, which imparts valuable insight into the Ottoman incorporation of the eastern frontier from the perspective of a native of the region. Bidlisi portrays the Ottoman reconquest of the fortress of Kemah in 1515 from the Kizilbash as an ideological triumph of Selim's policy of aggression against the Safavids, a policy signficantly thwarted by his father during his tenure as princely governor. While governor of Trabzon, sometime around 1502-1503, Selim had originally seized Kemah from Kizilbash supporters of Shah Ismail, along with other fortresses on the Georgian Trans-Caucasian frontier, including Ispiri, Kökez and Bayburt. In 1508, however, in an attempt to avoid war with the Safavids, Bayezid II ordered his son Selim to disband the garrisons and allow the Kizilbash to reoccupy the fortresses. The surrender of Kemah and surrounding fortresses significantly increased the tension between Selim and his father, a tension which culminated in warfare and Bayezid II's forced abdication of the throne in 1512. The Ottoman reconquest of the fortress thus represents also a triumph of Selim's original policy of aggression against the Kizilbash/Safavids rather than Bayezid II's ineffective attempt at accommodation.