The announcement in October 1908 of Austria-Hungary’s annexation of Bosnia and Herzegovina upset the fragile balance of power in the Balkans, enraging Serbia and pan-Slavic nationalists throughout Europe. Though weakened Russia was forced to submit, to its humiliation, its foreign office still viewed Austria-Hungary’s actions as overly aggressive and threatening. Russia's response was to encourage pro-Russian, anti-Austrian sentiment in Serbia and other Balkan provinces, provoking Austrian fears of Slavic expansionism in the region.