How did the assassination of Archduke Franz Ferdinand trigger World War I?

The assassination of Archduke Franz Ferdinand on June 28, 1914, served as the immediate catalyst for World War I. The act was carried out in Sarajevo by Gavrilo Princip, a Bosnian Serb nationalist associated with the Black Hand, a secret society seeking to liberate South Slavs from Austro-Hungarian rule.123

Austria-Hungary viewed the assassination as an opportunity to eliminate the threat posed by Serbia to the integrity of the Habsburg Empire. With the support of Germany, Austria-Hungary issued a deliberately provocative ultimatum to Serbia. When Serbia’s response was deemed insufficient, Austria-Hungary declared war on July 28, 1914.435

This local conflict rapidly escalated into a general European war through the activation of existing alliance systems, specifically the Triple Alliance and the Triple Entente. As nations mobilized to support their respective allies, the crisis triggered a chain reaction that engulfed the major powers of Europe.65