History of Bosnia and Herzegovina (1918–1941)

Following the war, Bosnia was incorporated into the South Slav kingdom of Serbs, Croats and Slovenes (soon renamed Yugoslavia). Political life in Bosnia at this time was marked by two major trends: social and economic unrest over property redistribution, and formation of several political parties that frequently changed coalitions and alliances with parties in other Yugoslav regions. The dominant ideological conflict of the Yugoslav state, between Croatian regionalism and Serbian centralization, was approached differently by Bosnia's major ethnic groups and was dependent on the overall political atmosphere. Although the initial split of the country into 33 oblasts erased the presence of traditional geographic entities from the map, the efforts of Bosnian politicians such as Mehmed Spaho ensured that the six oblasts carved up from Bosnia and Herzegovina corresponded to the six sanjaks from Ottoman times and, thus, matched the country's traditional boundary as a whole.

The establishment of the Kingdom of Yugoslavia in 1929, however, brought the redrawing of administrative regions into banates that purposely avoided all historical and ethnic lines, removing any trace of a Bosnian entity. Serbo-Croat tensions over the structuring of the Yugoslav state continued, with the concept of a separate Bosnian division receiving little or no consideration. The famous Cvetković-Maček agreement that created the Croatian banate in 1939 encouraged what was essentially a partition of Bosnia between Croatia and Serbia. However, outside political circumstances forced Yugoslav politicians to shift their attention to the rising threat posed by Adolf Hitler's Nazi Germany. Following a period of appeasement policies, signing of the Tripartite Treaty on March 25, 1941, and a coup d'état, Yugoslavia was finally invaded by Germany on April 6.