The radical land reforms advocated by Kočić only came to fruition after World War I, following the collapse of Austria-Hungary and the creation of the Kingdom of Serbs, Croats and Slovenes, which was later renamed the Kingdom of Yugoslavia. According to the historian Marko Attila Hoare, this caused the Muslim landowning class to further resent the Bosnian Serb peasantry and was one of the contributing factors behind the genocide of hundreds of thousands of Serbs by the Croatian nationalist Ustaše movement during World War II. The appeal of Kočić's political pronouncements among Bosnian Serbs extended across the political spectrum. During World War II, the Serbian nationalist Chetniks and the communist Partisans, both of whose members were predominantly Serbs, upheld Kočić as a hero. This manifested itself in the creation of the "Petar Kočić" Chetnik Detachment, under the command of Uroš Drenović. In Partisan propaganda, Kočić was lauded as an anti-German revolutionary who fought to liberate Bosnia and Herzegovina from foreign domination. During the socialist period, which lasted between 1945 and 1991, Kočić's Serb heritage was deliberately understated in schoolbooks, and schoolchildren were taught to regard him as an exclusively Bosnian historical and literary figure.