ボレスワフ4世
His first major intervention in Kievan Rus' affairs occurred in 1180, when the High Duke supported Vasylko, Prince of Shumsk and Drohiczyn (and son-in-law of the late Bolesław IV the Curly), and his nephew Leszek of Masovia in a dispute with Vladimir of Minsk for the region of Volhynia at Volodymyr-Volynsky. The war ended with the success of Vladimir, who conquered Volodymyr and Brest, while Vasylko held his ground at Drohiczyn.