Duchy of Münsterberg
In 1443, he formed an alliance with Archbishop Conrad of Wrocław and the Dukes of Wrocław, Jawor and Legnica against Hynek Krušina of Lichtenburg. Although Hynek had never given up his claims on Münsterberg, the dispute was resolved in 1444 and the Duchy of Münsterberg was granted to William, except the district of Ząbkowice Śląskie. The citizens of that district had fought on Hynek's side during the conflict and Hynek was allowed to retain the district.