Henryk IV Probus
In September 1277 King Ottokar II held in the border city of Opava a meeting of Polish princes. Sources doesn't specify either the exact date or the participants. Historians speculate only that they could be: Henryk IV Probus, Bolesław V the Chaste, Leszek II the Black, Władysław of Opole with his sons, Henry III of Głogów and Przemysł II. Several political decisions were made during the meeting, most notably military actions against Germany.