Siege of Dorostolon

During the course of the Rus'-Bulgarian war, Svyatoslav I of Kiev overran the eastern part of the First Bulgarian Empire and established his capital at Pereyaslavets on the Danube.

[5] There were several engagements before the walls of the city, which demonstrated to the Byzantines that the Rus' lacked skill in cavalry warfare.

[8] The Rus' felt they could not break the siege and agreed to sign a peace treaty with the Byzantine Empire, whereby they renounced their interests towards the Bulgarian lands and the city of Chersonesos in Crimea.

He was allowed to evacuate his army to Berezan Island, while the Byzantines entered Dorostolon and renamed it Theodoropolis, after the reigning empress Theodora.

Characteristically, Leo the Deacon attributes the victory to Saint Theodore Stratelates, who purportedly led the Byzantine army under the walls of Dorostolon.