What event triggered world war 1

The assasination of Franz Ferdinand

Explanation:

the immediate cause was the assassination of Franz Ferdinand, the archduke of Austria-Hungary. His death at the hands of Gavrilo Princip - a Serbian nationalist with ties to the secretive military group known as the Black Hand - propelled the major European military powers towards war.

World War One - Causes. The first world war began in August 1914. It was directly triggered by the assassination of the Austrian archduke, Franz Ferdinand and his wife, on 28th June 1914 by Bosnian revolutionary, Gavrilo Princip. This event was, however, simply the trigger that set off declarations of war.