Answer
Olga's son Sviatoslav came to power after his coming of age. This event occurred in 945, when Olga was assassinated by Drevlians who had been angered by her treatment of their leader, Mal. After Olga's death, Sviatoslav became the ruler of Kievan Rus' and continued his mother's policy of expansion. He conquered the steppes to the south and east, and established trade relations with the Byzantine Empire.