Nothing else is known of Boris II's life until 968, when he went to Constantinople again to negotiate a peace settlement with Emperor Nikephoros II Phokas, and apparently to serve as an honorary hostage. This arrangement was intended to put an end to the conflict between Bulgaria and Byzantium, who would now join forces against Prince Sviatoslav I of Kiev, whom the Byzantine emperor had pitted against the Bulgarians. In 969 a new Kievan invasion defeated the Bulgarians again and Peter I abdicated to become a monk. In circumstances that are not entirely clear, Boris II was allowed to return to Bulgaria and sit on his father's throne. ("The later Byzantine chronicle of John Skylitzes confounds this with a later event, in which Boris and his brother escaped Constantinople after the so-called rebellion of the Kometopouloi in Macedonia.")