969 – He became king of Bulgaria.
968 – He went to Constantinople again to negotiate a peace settlement with Emperor Nikephoros II Phokas, and apparently to serve as an honorary hostage.
– Boris II was unable to stem the Kievan advance, and found himself forced to accept Sviatoslav of Kiev as his ally and puppet-master, turning against the Byzantines.
970 – A Kievan campaign into Byzantine Thrace was defeated at Arkadioupolis, and the new Byzantine Emperor John I Tzimiskes advanced northwards. Failing to secure the defense of the Balkan passes, Sviatoslav allowed the Byzantines to penetrate into Moesia and lay siege to the Bulgarian capital Preslav.