Political map of Europe & the Mediterranean 10 September 1919 (Treaty of St. Germain): The Peace Treaty with Austria (Treaty of Saint-Germain-en-Laye (1919)) was signed on September 10, 1919. The Allies (Allies of World War I) recognized the independence of Czechoslovakia, the merging of Serbia with the southern Slavic nations to form Yugoslavia, and the expansion of Poland into former Austrian territory. Austria was also forbidden from uniting with Germany (Anschluss), something it had attempted to do after the war. The treaty with Hungary, the other part of Austria_Hungary (Austria-Hungary), was postponed by the outbreak of its war with Romania (Hungarian-Romanian War of 1919).