Zbruch River
With the collapse of Austria-Hungary following World War I in November 1918, Belz was included in the Western Ukrainian People's Republic. It came under Polish control in 1919 during the Polish-Ukrainian War. In April 1920, the Second Polish Republic, represented by Józef Piłsudski, and the Ukrainian People's Republic, represented by Symon Petlura signed the Treaty of Warsaw, in which they agreed that the Polish-Ukrainian border in Western Ukraine would follow the Zbruch River. This left Belz, along with the rest of Eastern Galicia in the Polish Republic.