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The catalyst for World War I, the assassination of Archduke Ferdinand of Austria and his wife, occurred on June 28, 1914. Despite military and diplomatic action immediately following the assassination, war was not officially declared for another month. On July 28, 1914 Austria-Hungary declared war on Serbia. In an almost domino effect, country after country followed suit, declaring war on each other throughout the month of August, until the majority of Europe was consumed. The United States did not enter the War until 1917. For a more thorough look at the outbreak of World War I, visit The Encyclopedia Britannica's website and their entry on World War I.

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10y ago

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