Who ruled over Bosnia in 1914 and why were Serbians not happy about it?

In 1914, Bosnia was ruled by the Austro-Hungarian Empire, which had annexed the region in 1908. Serbians were unhappy about this because Bosnia had a significant population of ethnic Serbs, and they viewed Austro-Hungarian control as an affront to Serbian nationalism and aspirations for unifying South Slavic peoples. The annexation intensified tensions in the Balkans and contributed to the outbreak of World War I, particularly after the assassination of Archduke Franz Ferdinand in Sarajevo by a Bosnian Serb nationalist.