Answer:
Austria-Hungary increased tension prior to WWI by announcing the annexation of Bosnia and Herzegovina in October of 1908.
Step-by-step explanation:
This act created a lot of diplomatic tension as there were many alliances across this region involving Russia, Germany, and the Ottoman Empire, for example. In addition, Serbia objected to the Austria-Hungary annexation as they were geographically close and ethnically tied to Bosnia and Herzegovina. The foreign minister of Russia had to support the Serbian claims because the Russian public was very critical of Austria. Austria-Hungary was supported however by the Germans and they backed the annexation and threatened aggression against Serbia unless Russia and Serbia conceded. Bosnia and Herzegovina had been under the control of the Ottoman Empire but Turkey was also experiencing its own forms of unrest and political instability. It was a period where many of the old regimes were being challenged.