The Kingdom of Yugoslavia was a country in Southeast and Central Europe that existed from 1918 until 1941. From 1918 to 1929, it was officially called the Kingdom of Serbs, Croats, and Slovenes, but the term "Yugoslavia" was its colloquial name due to its origins. The official name of the state was changed to "Kingdom of Yugoslavia" by King Alexander I on 3 October 1929.

Austria-Hungary, often referred to as the Austro-Hungarian Empire or the Dual Monarchy, was a multi-national constitutional monarchy in Central Europe between 1867 and 1918. Austria-Hungary was a military and diplomatic alliance of two sovereign states with a single monarch who was titled both emperor of Austria and King of Hungary. Austria-Hungary constituted the last phase in the constitutional evolution of the Habsburg monarchy: it was formed with the Austro-Hungarian Compromise of 1867 in the aftermath of the Austro-Prussian War and was dissolved shortly after Hungary terminated the union with Austria on 31 October 1918.