Who was assassinated, triggering the start of World War I?

The assassination of Archduke Francis Ferdinand is widely regarded as the catalyst that triggered the onset of World War I. On June 28, 1914, Ferdinand, the heir to the Austro-Hungarian throne, was killed in Sarajevo by Gavrilo Princip, a member of a nationalist group seeking independence for South Slavic peoples under Austro-Hungarian rule. This assassination set off a chain reaction of events that involved a complex web of alliances and treaties among European powers. Following the assassination, Austria-Hungary issued an ultimatum to Serbia, leading to the mobilization of larger forces and ultimately the declaration of war.

The significance of this event lies in its role in igniting existing tensions and rivalries between nations, leading to a full-scale war that changed the course of history. The other figures mentioned were not involved in this event; for instance, Adolf Hitler rose to prominence decades later, while Winston Churchill and Woodrow Wilson were key leaders during the war but were not directly connected to the cause of its outbreak.