The assassination of Archduke Franz Ferdinand triggered a chain reaction of war declarations that led to the start of World War I.
The military action that led to the start of World War I was the assassination of the Austrian Archduke Franz Ferdinand in 1914. This event triggered a chain reaction of war declarations, with Austria-Hungary declaring war on Serbia, followed by Russia declaring war on Austria-Hungary, and then Germany declaring war on Russia and France. The Great War began as a result of these interconnected alliances and conflicts.
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