Hultschiner Ländchen
In 1918, the former Duchy formed part of the newly created state of Czechoslovakia, except the Cieszyn Silesia, which was split between Czechoslovakia and Poland in 1920, Czechoslovakia gaining its western portion. Hlučín Region (, ), formerly part of Prussian Silesia, also became part of Czechoslovakia under the Treaty of Versailles in 1920.