The assassination of Archduke Franz Ferdinand was a contributing factor to the start of the First World War as tensions raised between the Serbians and the Austro-Hungarians.
Austria-Hungary decided to stamp its authority in the Balkan state by hoping to crush the Nationalist movement of the Black Hand Serbian Nationalists.
Austria-Hungry Issued a ultimatum to the Serbians that the Guilty party to Franz Ferdinand’s death should be brought to Justice.
With the Serbians having Slavic ties with the Russians, this was a major concern to the Austria-Hungarians although the Russians were not expected to get involved.
Austria-Hungary turned to its nearest ally Germany for assurance that if the Russians declared war on Austria-Hungary that the Germans would come to the aid of Austrian-Hungary.
The Germans gave reassurance that they would support Austria-Hungary as Austria Hungary declared war on Serbia on 28th July 1914.