History of Europe

What specific event sparked the start of world war 1 in Europe?

The assassination of Archduke Franz Ferdinand of Austria, heir to the Austro-Hungarian throne, by a Serbian nationalist named Gavrilo Princip on June 28, 1914, in Sarajevo, the provincial capital of Bosnia-Herzegovina (formally annexed by Austria-Hungary in 1908), is widely considered the catalyst that set off a chain of events leading to the outbreak of World War I.