<P> The trigger for the war was the assassination of Archduke Franz Ferdinand of Austria , heir to the throne of Austria - Hungary , by Yugoslav nationalist Gavrilo Princip in Sarajevo on 28 June 1914 . This set off a diplomatic crisis when Austria - Hungary delivered an ultimatum to the Kingdom of Serbia and , as a result , entangled international alliances formed over the previous decades were invoked . Within weeks the major powers were at war , and the conflict soon spread around the world . </P>
<P> The trigger for the war was the assassination of Archduke Franz Ferdinand of Austria , heir to the throne of Austria - Hungary , by Yugoslav nationalist Gavrilo Princip in Sarajevo on 28 June 1914 . This set off a diplomatic crisis when Austria - Hungary delivered an ultimatum to the Kingdom of Serbia and , as a result , entangled international alliances formed over the previous decades were invoked . Within weeks the major powers were at war , and the conflict soon spread around the world . </P>
why did the first world war broke out
why did the first world war broke out
assassination of Archduke Franz Ferdinand of Austria , heir to the throne of Austria - Hungary , by Yugoslav nationalist Gavrilo Princip in Sarajevo on 28 June 1914 assassination of
assassination of Archduke Franz Ferdinand of Austria , heir to the throne of Austria - Hungary , by Yugoslav nationalist Gavrilo Princip in Sarajevo on 28 June 1914 assassination of