The Battle at the Mouth of the Danube

A new power appeared in the Balkans during this period: Kievan Rus', which allied with Byzantium. In August 968, Prince Sviatoslav of Kiev, encouraged by Byzantium, invaded Bulgaria with an army of sixty thousand and defeated a Bulgarian force half that size, which withdrew to Silistra.

Tsar Peter suffered an epileptic seizure, abdicated, retired to a monastery and died soon afterwards. Following his death on 30 January 969, his son Boris ascended the throne.