Serbian nationalism asserts that Serbs are a nation and promotes the cultural unity of Serbs. It is an ethnic nationalism. Originally arising in the context of the general rise of nationalism in the Balkans under Ottoman rule, under the influence of Serbian linguist Vuk Stefanović Karadžić and Ilija Garašanin.Serbian nationalism was an important factor during the Balkan Wars which contributed to the decline of the Ottoman Empire, during World War I, and again during the breakup of Yugoslavia and the Yugoslav Wars of the 1990s.After 1878, Serbian nationalists merged their goals with those of Yugoslavists, and emulated the Piedmont's leading role in the Risorgimento of Italy, by claiming that Serbia sought not only to unite all Serbs in one state, but that Serbia intended to be a South Slavic Piedmont that would unite all South Slavs in one state known as Yugoslavia. Serbian nationalists supported a centralized Yugoslav state that guaranteed the unity of the Serbs while resisting efforts to decentralize the state. The St. Vitus Day Constitution adopted by Yugoslavia in 1920, consolidated the country as a centralized state under the Serbian Karađorđević monarchy. Others in Yugoslavia opposed the centralized state and demanded decentralization, including Croatian nationalists who demanded an autonomous Croatia within Yugoslavia, that was accepted by the Yugoslav government in the Cvetković–Maček Agreement of 1939. Serbian nationalists opposed the agreement on the grounds that it weakened the unity of Serbdom, asserting its importance to Yugoslavia with the slogan ""Strong Serbdom, Strong Yugoslavia"". The invasion and partition of Yugoslavia in World War II, resulted in violent ethnic conflict between nationalist Serbs, Croats, Bosniaks, and others, resulting in a highly violent sectarian variant of Serbian nationalism rising in the Chetnik movement.The decentralization of the Socialist Federal Republic of Yugoslavia in the 1960s and the suppression of all ethnic nationalist sentiments led to a Serbian nationalist backlash and resurgence in the 1980s, that condemned post-World War II Yugoslavism and the decentralization of Yugoslavia. Upon Yugoslavia collapsing in the 1990s with multiple republics seeking secession, Serbian nationalists demanded that all Serbs in all the Yugoslav republics had the right to be united in a common state, ethnic conflict occurred between Serbs seeking unity with Serbia and other Yugoslav ethnicities seeking independence.