When was the annexation of Bosnia finally approved by Serbia ?
In 1908 , the Austria 's foreign minister , Alois von Aehrenthal , made a secret deal with the Russian foreign minister , Alexander Izvolsky in which the Russians would not oppose the annexation of Bosnia and Herzegovina in exchange for the opening of the Bosporus Strait and the Dardanelles to Russian warships , an amendment of the 1878 Treaty of Berlin .