Croatia sided with the Austrians, Ban Josip Jelačić helping defeat the Hungarian forces in 1849, and ushering a period of Germanization policy. By the 1860s, failure of the policy became apparent, leading to the Austro-Hungarian Compromise of 1867 and creation of a personal union between the crowns of the Austrian Empire and the Kingdom of Hungary. The treaty left the issue of Croatia's status to Hungary, and the status was resolved by the Croatian–Hungarian Settlement of 1868, when kingdoms of Croatia and Slavonia were united. The Kingdom of Dalmatia remained under de facto Austrian control, while Rijeka retained the status of Corpus separatum introduced in 1779. After Austria-Hungary occupied Bosnia and Herzegovina following the 1878 Treaty of Berlin, the Croatian Military Frontier was abolished and the territory returned to Croatia in 1881, pursuant to provisions of the Croatian-Hungarian settlement. Renewed efforts to reform Austria-Hungary, entailing federalisation with Croatia as a federal unit, were stopped by advent of World War I.
Kingdom of Yugoslavia and World War II
On 29 October 1918 the Croatian Sabor declared independence and decided to join the newly formed State of Slovenes, Croats and Serbs, which in turn entered into union with the Kingdom of Serbia on 4 December 1918 to form the Kingdom of Serbs, Croats, and Slovenes. The 1921 constitution defining the country as a unitary state and abolition of historical administrative divisions effectively ended Croatian autonomy. The new constitution was opposed by the most widely supported national political party—the Croatian Peasant Party (HSS) led by Stjepan Radić. The political situation deteriorated further as Radić was assassinated in the National Assembly in 1928, leading to the dictatorship of King Alexander in January 1929. The dictatorship formally ended in 1931 when the king imposed a more unitarian constitution, and changed the name of the country to Yugoslavia. The
