In 1443 he expressed his consent to the sale of the Duchy of Siewierz to Zbigniew Oleśnicki, Bishop of Kraków, in return for which he received from Wenceslaus I the amount of 500 pieces of silver.
In his will, he left his domains – half of both Głogów and Ścinawa – to his widow Margareta of Celje (as her bequest, dower) and Przemysław II, who actually took effective power over all the lands.
In 1466 the prince took an active part in the expedition of George of Podebrady to Kłodzko (Kladsko), causing tension between Cieszyn and the powerful Wrocław (Breslau).
Trying to shift between Poland, Bohemia and Hungary, in 1473 Przemysław II supported Matthias Corvinus in his war against Duke Wenceslaus III of Rybnik.
In 1474 Wenceslaus I, the last surviving brother of Przemysław II, died without issue, allowing him to unify all their domains under his rule (except Siewierz and Bytom, which were already sold).
Przemysław II's growing importance, however, didn't please Bohemian-Hungarian king Matthias Corvinus, who, during the meeting of Racibórz in 1475, obtained from Casimir IV of Poland the guarantee that he could interfere without difficulties in the sovereignty over the Duchy of Teschen, threatening to completely deprive Przemysław II if he didn't pay a huge contribution.
The Duke was saved from a final fall against the Hungarian-Polish army expedition, thanks to Jakub z Dębna, who supported the defense of Cieszyn.