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Austria-Hungary
On July 28, 1914, one month to the day after Archduke Franz Ferdinand of Austria and his wife were killed by a Serbian nationalist in Sarajevo, Austria-Hungary declares war on Serbia, effectively beginning the First World War. -
Germany
During World War I, the German Empire was one of the Central Powers that lost the war. It began participation in the conflict after the declaration of war against Serbia by its ally, Austria-Hungary. -
Ottoman Empire
The Ottoman Empire participated in World War I as one of the Central Powers. The Ottoman Empire entered the war by carrying out a surprise attack on Russia's Black Sea coast on 29 October 1914, with Russia responding by declaring war on 5 November 1914. -
Bulgaria
The Kingdom of Bulgaria participated in World War I on the side of the Central Powers from 14 October 1915, when the country declared war on Serbia, until 30 September 1918, when the Armistice of Thessalonica came into effect.