The Byzantines were unable to exploit this victory or pursue the remnants of the Rus' army, since Bardas Phokas rose in revolt in Asia Minor. Bardas Skleros and his men were consequently withdrawn to Asia Minor, whilst Sviatoslav restricted his forces to the north of the Balkan Mountains. In the spring of the next year, however, with Phokas' rebellion subdued, Tzimiskes himself, at the head of his army, advanced north into Bulgaria. The Byzantines took the Bulgarian capital Preslav, capturing the Bulgarian tsar Boris II, and confined the Rus' in the fortress of Dorostolon (modern Silistra). After a three-month siege and a series of pitched battles before the city walls, Sviatoslav conceded defeat and abandoned Bulgaria.