Casimir II the Just
In 1166 Mieszko III and his brothers started another Prussian crusade, whereby Duke Henry of Sandomierz was killed in battle in October of that year. Before his departure, and in case of his death, he had left his duchy to his youngest brother Casimir II the Just, who by their father's testament had remained without lands. However, High Duke Bolesław IV, against his late brother's will, occupied Sandomierz and annexed it to his Seniorate Province.