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the assassination of Archduke Franz Ferdinand and his wife, Sophie, on June 28, 1914, by a Serbian nationalist named Gavrilo Principle directly triggered a series of events that led to World War I
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key fact about the Second Battle of Ypres is that it marked the first large-scale use of poison gas as a weapon on the Western Front.
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The Second Battle of Ypres took place in 1915 during the First World War, from April 22 to May 25, 1915. It was a significant battle because it marked the first large-scale use of poison gas on the Western Front, which was a new and horrific tactic in modern warfare.