Which archduke's assassination in Sarajevo triggered World War I?

The assassination of Archduke Franz Ferdinand in Sarajevo triggered the chain of events that began World War I.

Franz Ferdinand was the heir presumptive to the throne of Austria-Hungary. On 28 June 1914, Bosnian Serb student Gavrilo Princip shot the archduke and his wife, Sophie, Duchess of Hohenberg, during a motorcade in Sarajevo. Their deaths inflamed existing tensions involving nationalism, imperial rivalry, militarism, and Europe’s rigid alliance system.

Austria-Hungary blamed Serbia and issued a severe ultimatum. After diplomatic negotiations failed, Austria-Hungary declared war on Serbia on 28 July. Russia mobilized in support of Serbia, Germany backed Austria-Hungary and declared war on Russia and France, and Britain entered after Germany invaded neutral Belgium.

The assassination did not by itself make a general European war inevitable; it acted as the spark in a highly combustible political environment. A common mix-up is confusing Franz Ferdinand with Kaiser Wilhelm II, who was Germany’s emperor during the war, or with Emperor Franz Joseph, Franz Ferdinand’s uncle and predecessor.