What was the conflict between Austria, Hungary, and Serbia?

From the beginning of the occupation Austria-Hungary counted upon ultimately obtaining permanent possession. Serbia, however, continued to hope that the provinces, or at least such a portion of them as would give access to the Adriatic, would some day be to her. The crisis in 1908-1909 sprang from the fact that Serbia believed that she must prevent the consummation of annexation by Austria-Hungary or give up permanently her long-cherished hopes.

Soon after the proclamation of annexation Serbia called a part of the reserves to the colors and lodged a vigorous protest with the powers, demanding either a return to the status quo ante or compensations calculated to assure the independence and material progress of Serbia. Serbian newspapers demanded a strip of territory extending across Novi-Bazar and Bosnia-Herzegovina to the Adriatic. The Government of the Dual Monarchy refused to receive the Serbian protest. It denied that Serbia had any right to raise a question as to the annexation.

The immediate cause of the war was the assassination of Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, by Gavrilo Princip, a Bosnian Serb citizen of Austria-Hungary and member of the Black Hand. This group wanted to have an independent Serbia from Austria-Hungary.