Bolesław I's intervention in the Kievan succession crisis
The intervention in the Kievan succession crisis of 1015–1019 by the Polish ruler Bolesław the Brave was an episode in the struggle between Sviatopolk I Vladimirovich ("the Accursed") and his brother Yaroslav ("the Wise") for the rulership of Kiev (Kyiv) and Kievan Rus'. It occurred when Sviatopolk's father-in-law Bolesław, ruler of Poland, intervened on Sviatopolk's behalf.