Болеслав I Храбрый
When Sviatopolk was eight years old, Vladimir put him in charge of Turov and later arranged his marriage with the daughter of the Polish duke Bolesław I Chrobry of Poland. The young princess came to Turov together with Reinbern, the Bishop of Kolberg (now Kołobrzeg). Dissatisfied with Vladimir and encouraged by his own wife and Reinbern, Sviatopolk began preparations for war against Vladimir, probably counting on support from his father-in-law. Vladimir soon discovered Sviatopolk's intentions, however, and threw him, his wife and Reinbern in prison, where Reinbern died.