Prior to the First World War, the territory that forms modern day Slovenia was part of the Austro-Hungarian Empire. To appease separatist ambitions of Slavic nations in the Austrian part of the empire, Emperor Karl, in the final days of the First World War, offered to reform Austria into a federal union, with Slovenia becoming one of the federal states in a new Austria. The Slovenian political leadership rejected the offer, declared independence from the Habsburg monarchy and formed the State of Slovenes, Croats, and Serbs, which a month later merged with the Kingdom of Serbia and became the Kingdom of Serbs, Croats, and Slovenes a. k. a. Yugoslavia.