The assassination of Austria-Hungary´s heir presumptive archduke Franz Ferdinand d’Este by the Serbian student Gavrilo Princip occurred on 28 June 1914 in Sarajevo. The assassination conspirators co-operated with the secret Serbian society Unification or Death (Black Hand) and were led by Dragutin Dimitrijevic, Colonel of Serbia´s General Staff. Alongside Franz Ferdinand died his wife, Sophi Chotek, who was sitting with him in the car. Austria-Hungary failed to take advantage of the intitial response to the assassination, and on 23 July 1914 submitted an ultimatum to Serbia that Belgrade refused. Then Austria-Hungary, supported by Germany, declared war on Serbia, an immediate impetus for the outbreak of World War I.