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28/07/1914 Austrian empire declares war on Serbia

9:10

How World War I Started: Crash Course World History 209

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Life in a Trench | World War I | History

11:45

Archdukes, Cynicism, and World War I: Crash Course World History #36

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Epic History: World War One - 1914

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Who Started World War I: Crash Course World History 210

The trigger for the war was the assassination of Archduke Franz Ferdinand of Austria. This set off a diplomatic crisis when Austria-Hungary delivered an ultimatum to the Kingdom of Serbia. Within weeks the major powers were at war, and the conflict soon spread around the world.