The assassination of Archduke Franz Ferdinand in June 1914 sparked World War I. This incident, carried out by Gavrilo Princip, a member of a nationalist group, escalated existing tensions in Europe. Ferdinand's assassination set off a chain reaction of alliances and mutual defense agreements, leading Austria-Hungary to declare war on Serbia. The conflict quickly involved other major powers, including Germany, Russia, and France, resulting in a global war that lasted until 1918. The consequences of World War I were profound, reshaping national boundaries and setting the stage for further conflicts in the 20th century.