Austria did not single-handedly start the war. The assassination of Archduke Franz Ferdinand, the heir to the Austro-Hungarian throne, by a Bosnian Serb nationalist in Sarajevo, Bosnia, on June 28, 1914, is often cited as the immediate cause of World War I. Austria-Hungary responded to the assassination by issuing an ultimatum to Serbia, which led to a chain reaction of events involving other European powers, ultimately leading to the outbreak of war.
