The Treaty of Saint-Germain-en-Laye was a crucial agreement following World War I, involving the Republic of German-Austria, which sought to formalize its status and territorial limits in the wake of the Austro-Hungarian Empire's collapse. Signed in Saint-Germain-en-Laye, France, on September 10, 1919, the treaty included significant territorial losses for Austria. Key provisions included the ceding of South Tyrol to Italy and the recognition of the new states of Czechoslovakia and Yugoslavia, greatly redrawing the map of Europe. The treaty was part of a series of peace settlements aimed at establishing the post-war order and was heavily influenced by the ideology of self-determination proposed by U.S. President Woodrow Wilson.

The treaty also included clauses on disarmament and the guarantee of rights for ethnic minorities in the newly established states. Austria was limited in its military capabilities and mandated to accept the new geopolitical reality without the ability to unify with Germany. This left the Republic of German-Austria diminished in size and influence, as it became a smaller nation surrounded by newly formed neighbors. These changes were met with mixed reactions by the nationalistic sentiments that had been strong during the war, leading to both hope and discontent among various ethnic groups.

The signing of the Treaty of Saint-Germain-en-Laye underscored the realization that the old world order was irreversibly changed and set the stage for future tensions in Central and Eastern Europe. The territorial adjustments made at this conference contributed to tensions that would later lead to further conflicts in the region.