The
Bosnian crisis of 1908–09, also known as the
Annexation crisis or the
First Balkan Crisis, erupted when on 6 October 1908,
Austria-Hungary announced the
annexation of
Bosnia and Herzegovina, territories formally within the sovereignty of the
Ottoman Empire. This unilateral action—timed to coincide with
Bulgaria's declaration of independence (5 October) from the Ottoman Empire—sparked protestations from all the
Great Powers and Austria-Hungary's Balkan neighbours,
Serbia and
Montenegro. In April 1909 the
Treaty of Berlin was amended to reflect the
fait accompli and bring the crisis to an end. The crisis permanently damaged relations between Austria-Hungary on one hand and Serbia, Italy and the
Russian Empire on the other. The Italian historian
Luigi Albertini regarded it as laying the grounds for
World War I. Although the crisis ended with what appeared to be a total Austro-Hungarian diplomatic victory, Russia became determined not to back down again and hastened its military build-up. Austrian–Serbian relations became permanently stressed.