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1914
June 28: Franz Ferdinand, heir to the Austro-Hungarian throne, is assassinated by Serbian youths in Sarajevo, which becomes the trigger for World War I.
July-august: European powers declare war and World War I breaks out. At this time, President Woodrow Wilson announced that the United States would remain neutral. -
1915
Germany began a strategy of "unrestricted submarine warfare," which resulted in losses of merchant ships from many countries, including the United States. The United States is strongly displeased. -
1916
A series of incidents, such as German attempts to instigate a Mexican attack on the United States (the "Zimmerman cables" incident) and the Florida bombing (though it was later proved false), increased American resentment and hostility toward Germany. -
1917
January: President Wilson addresses Congress with the Fourteen Points,
February-march: As the war situation worsens and tensions between the United States and Germany continue,
April 2: President Wilson asks Congress for authorization to declare war on Germany,
April 6 - The United States Congress passes a resolution declaring war on Germany, officially entering World War I. -
1918
With the participation of the United States, the Allies (including Britain, France, Russia, etc.) gradually gained an advantage on the battlefield.
November 11: Germany, under pressure from the Allies, is forced to sign an Armistice, officially ending World War I.