sentences:  The duchy's capital was Bytom ("Beuthen"), formerly part of Lesser Poland until in 1177 the Polish High Duke Casimir II the Just had attached it to the Silesian Duchy of Racibórz.When Władysław's second son Casimir became Duke of Bytom, he at first ruled jointly with his brother Duke Bolko I of Opole and from 1284 on alone.The conflict with his Piast cousin Duke Henryk IV Probus of Silesia-Wrocław led Casimir to seek shelter from King Wenceslaus II of Bohemia and in 1289 he became the first Silesian Piast duke to submit himself under Bohemian overlordship.