nationalist Party of Rights (HSP) in 1861. Unlike Strossmayer and the proponents of the Illyrian movement, HSP advocated a united Croatia that stood independently of a Pan-Slavic umbrella state. Starčević was an early opponent of Croatia's unification with Serbs and Slovenes (chiefly the Kingdom of Serbia); their ideologies gradually gained popularity during the interwar period as tensions grew in the Kingdom of Yugoslavia between the Croatian and the more influential Serbian political leaders. Ensuing events surrounding the ideology culminated in the World War II conflict between the Independent State of Croatia and its opponents including Chetnik Serbs and Communists of all ethnicities (including Croatian). Cvetković–Maček Agreement Amid rising ethnic tensions between Croats and Serbs in the 1930s, an autonomous state within Yugoslavia, called the Banovina of Croatia was peacefully negotiated in the Yugoslav parliament via the Cvetković–Maček Agreement of 1939. Croatia was united into a single territorial unit and was provided territories of parts of present-day Vojvodina, and both Posavina and southern parts of present-day Bosnia and Herzegovina, which had Croatian majority at the time. Independent State of Croatia The first modern development of a Greater Croatia came about with the establishment of the Independent State of Croatia (, NDH). Following occupation of the country by Axis forces in 1941, Slavko Kvaternik, deputy leader of the Ustaše proclaimed the establishment of the NDH. The Ustaša, an ultranationalist and fascist movement founded in 1929 supported a Greater Croatia that would extend to the River Drina and to the edge of Belgrade. Ante Pavelić, the Ustaše's Poglavnik (leader) had been in negotiations with Fascist Italy since 1927. These negotiations included Pavelić supporting Italy's annexation of its claimed territory in Dalmatia in exchange for Italy supporting an independent Croatia. In addition, Mussolini offered Pavelić the right for Croatia to annex all of Bosnia and Herzegovina. Pavelić agreed to this exchange. The Greater Croatia ideology, combined with Nazi racial theory, culminated in the Genocide of Serbs and the Holocaust in NDH carried out by Ustaša. Bosnian War The most recent expression of a Greater Croatia arose in the aftermath of the breakup of Yugoslavia. When the multiethnic Yugoslav republic of Bosnia and Herzegovina declared independence in 1992, Bosnian Serb political representatives, who had boycotted the referendum, established their own government of Republika Srpska, whereupon their forces attacked the Republic of Bosnia and Herzegovina. At the beginning of the Bosnian war, the Croats and Bosniaks