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[Archduke Ferdinand][https://www.history.com/this-day-in-history/archduke-ferdinand-assassinated]
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[Austria declares war on Serbia][https://www.history.com/this-day-in-history/austria-hungary-declares-war-on-serbia]
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[The Battle of Somme][https://www.history.com/topics/world-war-i/battle-of-the-somme]
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[United Stated declares war against Germany][https://www.army.mil/article/7916/us_declares_war_on_germany]
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[United States declare war against Austria-Hungary][https://www.centenarynews.com/article/the-us-declares-war-on-austria-hungary-7-december-1917]
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