Young Bosnia
On 28 June 1914, Franz Ferdinand and his wife were assassinated in Sarajevo by the 19-year-old Gavrilo Princip, a member of Young Bosnia. Franz Ferdinand's assassination led to the July Crisis and precipitated Austria-Hungary's declaration of war against Serbia, which in turn triggered a series of events that eventually led to Austria-Hungary's allies and Serbia's allies declaring war on each other, starting World War I.