Archduke François Ferdinand (1863-1914), the nephew of Emperor François Joseph I and Empress 'Sissi' became heir to the Austro-Hungarian throne after the death of their son, Crown Prince Rudolph, in 1889. At a time of political instability, the Archduke and his wife, Duchess von Hohenberg, were assassinated during a visit to Sarajevo in June 1914. Their assassin, Gavrilo Princip, a member of the Black Hand, was one of many people living in Bosnia-Herzegovina who were unhappy with Austrian rule and favoured union with Serbia. The assassination led the Austro-Hungarian Empire and its ally Germany into the First World War against Serbia, Russia, France and Great Britain.