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Archduke Franz Ferdinand is assassinated in Sarajevo. His death is the lead to World War 1.
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Germany invades Belgium, starting World War 1.
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The First Battle of the Marne begins. Trench warfare begins as soldiers on both sides dig in.
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The Germans fire shells filled with chlorine gas at Allied lines. This is the first time that large amounts of gas are used in battle with a result of a near-collapse of the French lines.
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A German submarine sinks the Lusitania. The ship carries 1,198 people, 128 of them Americans.
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Tsar Nicholas II takes personal control over Russia's armies.
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The Battle of Verdun begins. The Battle of Verdun was the longest battle of World War I and was one of the bloodiest.
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The British employ the first tanks ever used in battle, at Delville Wood. Although they are useful at breaking through barbed wire and clearing a path for the infantry, tanks are still primitive and they fail to be the decisive weapon.
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Germany sends the secret Zimmerman Telegram to Mexico to convince Mexico to join the war. The British intercept and decipher the coded message.
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April 6 - The United States declares war on Germany.
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The Bolsheviks successfully overthrow the Russian government during the 1917 Russian Revolution.
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U.S. President Woodrow Wilson issues his Fourteen Points to peace.
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Russia signs the Treaty of Brest Litovsk, which is a peace treaty between Russia and the Central Powers.
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Germany signs the armistice at France. Fighting ends on the 11th hour of the 11th day of the 11th month.
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The Treaty of Versailles officially ends WWI.
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