The assassination of Archduke Franz Ferdinand on June 28, 1914, triggered the outbreak of World War I. Ferdinand, heir to the Austro-Hungarian Empire, was killed by a Serbian nationalist, leading Austria-Hungary to issue an ultimatum to Serbia. The complex web of alliances in Europe resulted in a rapid escalation of tensions, drawing multiple nations into the conflict. This event not only set off a global war but also marked the beginning of significant geopolitical changes, ultimately leading to the collapse of empires and paving the way for future conflicts and the reshaping of international relations.