The assassination of Archduke Franz Ferdinand in 1914 triggered World War I. The Archduke, heir to the Austro-Hungarian throne, was killed in Sarajevo by Gavrilo Princip, a member of a nationalist group seeking independence for Bosnia. His assassination set off a chain reaction of alliances and treaties, leading to a declaration of war by Austria-Hungary against Serbia. This event escalated tensions among major European powers, resulting in widespread conflict that involved many nations. The war ultimately reshaped borders, led to the fall of empires, and set the stage for significant political and social changes in the 20th century.