The common rule between them lasted until 1284, when they decided to make a formal division of their domains: Casimir took the towns of Bytom (the main city and now capital of his Duchy), Koźle, Toszek, Gliwice and Siewierz.
The cause of the bad relations between Władysław Opolski's sons and the Duke of Wrocław possibly started when Henry IV repudiated his wife Constance (sister of the Opole-Racibórz brothers) and sent her back home.
In any event, the Dukes of Cieszyn and Racibórz soon followed the example of Casimir and also paid homage to the Kingdom of Bohemia (some historians believed that this could be the cause of the bloody Battle of Siewierz on 26 February of that year).
In 1303, Casimir decided to give his sons separate districts, which further helped to reduce the already small Duchy of Bytom: Bolesław received Toszek and Władysław obtained Koźle.
The extinction of the Přemyslid dynasty after the death of King Wenceslaus III in 1306 caused the Duke of Bytom to stop his homage to the Bohemian crown.