The event that sparked the beginning of World War 1 was the assassination of Archduke Franz Ferdinand of Austria, heir to the Austro-Hungarian throne. He and his wife, Sophie, Duchess of Hohenberg, were shot dead on 28 June 1914 in Sarajevo, the provincial capital of Bosnia-Herzegovina (formally annexed by Austria-Hungary in 1908). The assassin, Gavrilo Princip, was a Bosnian Serb nationalist and member of the Black Hand, a secret society dedicated to liberating Bosnia-Herzegovina from Austro-Hungarian rule.
The assassination triggered a chain of events leading to the outbreak of World War 1. Firstly, Austria-Hungary issued a ultimatum to Serbia, which was largely seen as unacceptable. Serbia agreed to most of the terms, but not all, which prompted Austria-Hungary to declare war on Serbia. Russia, which had close cultural and religious ties with Serbia and saw Austria-Hungary's move as a threat to its influence in the Balkans, began mobilizing its troops in support of Serbia. Germany, allied with Austria-Hungary, declared war on Russia and France (Russia's ally) in response. Eventually, many European countries were drawn into the conflict, marking the beginning of World War 1.