The event marked by the assassination of Archduke Franz Ferdinand was the outbreak of World War I. The archduke, heir to the Austro-Hungarian throne, was assassinated on June 28, 1914, in Sarajevo by Gavrilo Princip, a member of a nationalist group seeking independence for Slavic peoples. This act set off a chain reaction of alliances and tensions among European powers, leading to the mobilization of armies and declarations of war. World War I, lasting from 1914 to 1918, resulted in unprecedented destruction, the collapse of empires, and significant geopolitical shifts, profoundly altering the course of history.