Franz Ferdinand and his wife Sophie were assassinated, ultimately causing World War I.
Archduke Franz Ferdinand was next in line for the Austro-Hungarian throne and a major proponent of peace within the empire. Bosnian Serbs and Serbian secret military organization the Black Hand were behind the assassination, so the Austro-Hungarian Empire blamed Serbia. After much back-and-forth, war was declared on Serbia. Within a short time, all of Europe’s greatest powers had chosen a side, and World War I began.