The Byzantine Emperor Alexios III Angelos made Ivanko the commander of Philippopolis (now Plovdiv in Bulgaria). Ivanko seized two fortresses in the Rhodopi Mountains from Kaloyan, but by 1198 he had made an alliance with him. Cumans and Vlachs from the lands to the north of the river Danube broke into the Byzantine Empire in the spring and autumn of 1199. Choniates, who recorded these events, did not mention that Kaloyan cooperated with the invaders, so it is likely that they crossed Bulgaria without his authorization. Kaloyan captured Braničevo, Velbuzhd, Skopje and Prizren from the Byzantines, most probably in that year, according to historian Alexandru Madgearu.