It is not until 879 that the name Ioannina appears for the first time, in the acts of the Fourth Council of Constantinople, which refer to one Zacharias, Bishop of Ioannine, a suffragan of Naupaktos. After the Byzantine conquest of Bulgaria, in 1020 Emperor Basil II subordinated the local bishopric to the Archbishopric of Ohrid. The Greek archaeologist K. Tsoures dated the Byzantine city walls and the northeastern citadel of the Ioannina Castle to the 10th century, with additions in the late 11th century, including the south-eastern citadel, traditionally ascribed to the short-lived occupation of the city by the Normans under the leadership of Bohemond of Taranto in 1082. In a chrysobull to the Venetians in 1198, the city is listed as part of its own province ("provincia Joanninorum" or "Joaninon"). In the treaty of partition of the Byzantine lands after the Fourth Crusade, Ioannina was promised to the Venetians, but in the event, it became part of the new state of Epirus, founded by Michael I Komnenos Doukas.