“ In a series of campaigns against the newly established Russian power (970–973) he drove the enemy out of Thrace, crossed Mt Haemus and besieged the fortress of Dorystolon on the Danube. In several hard-fought battles he broke the strength of the Russians so completely that they left him master of eastern Bulgaria. He further secured his northern frontier by transplanting to Thrace some colonies of Paulicians whom he suspected of sympathising with their Saracen neighbours in the east. ”