The assassination of Archduke Franz Ferdinand of Austria-Hungary in June 1914 triggered World War I. This event set off a chain reaction of alliances and hostilities among the major powers of Europe, leading to full-scale war. The tensions that had been building due to nationalism, imperialism, and militarism found an explosive outlet in the archduke's death. Consequently, countries across Europe entered into conflict, which ultimately expanded around the globe, reshaping international relations and altering the geopolitical landscape for decades to come.