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Franz Ferdinand was assassinated
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Russia announces mobilisation of their army
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Austria-Hungary declares war on Serbia
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• Germany, allied to Austria-Hungary by treaty, viewed the Russian mobilisation as an act of war against Austria-Hungary, and after scant warning declared war on Russia on 1 August.
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• France, bound by treaty to Russia, found itself at war against Germany and, by extension, on Austria-Hungary following a German declaration on 3 August. Germany was swift in invading neutral Belgium so as to reach Paris by the shortest possible route.