Greater Serbia the Kingdom of Serbia retreated from Durrës in April 1913 under pressure of the naval fleet of Great Powers, but it remained in other parts of Albania for the next two months. The secret military society called Unity or Death, popularly known as the Black Hand, headed by Serbian colonel Dragutin Dimitrijević Apis, which took an active and militant stance on the issue of a Greater Serbian state. This organization is believed to have been responsible for numerous atrocities following the Balkan Wars in 1913. In 1914, Young Bosnia member Gavrilo Princip assassinated Archduke Franz Ferdinand in Sarajevo, which set
Serbs internationally until the Congress of Berlin in 1878. Serbia fought in the Balkan Wars of 1912–13, which forced the Ottomans out of the Balkans and doubled the territory and population of the Kingdom of Serbia. In 1914, a young Bosnian Serb student named Gavrilo Princip assassinated Archduke Franz Ferdinand of Austria, which directly contributed to the outbreak of World War I. In the fighting that ensued, Serbia was invaded by Austria-Hungary. Despite being outnumbered, the Serbs subsequently defeated the Austro-Hungarians at the Battle of Cer, which marked the first Allied victory over the Central Powers in the war. Further victories