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Gavrilo Princip, who has ties to the Serbian terrorist-type group the Black Hand, assassinates Archduke Franz Ferdinand of Austria-Hungary.
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Austria-Hungary declares war on Serbia.
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Ottoman Empire (Turkey) and Germany sign a secret treaty of alliance.
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Germany invades Belgium. President Woodrow Wilson declares that the United States is neutral. Britain declares war on Germany.
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Austria-Hungary invades Russia, opening the fighting on the Eastern Front.
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Russia declares war on Ottoman Empire (now Turkey).
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A German U-20 submarine sinks the British passenger ship, the Lusitania; 1,198 are killed, including 128 Americans.
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First Battle of the Somme River, France. The British introduce the tank.
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American troops begin landing in France.
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Germany accepts the armistice terms demanded by the Allies, ending the war.
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The Treaty of Versailles is signed at the Palace of Versailles, France.