The sinking of Lusitania
the sinking of the Lusitania ;
The entry of the United States into World War I was hastened primarily by the Zimmerman Note, which proposed a military alliance with Mexico against the U.S. This, combined with Germany's policy of unrestricted submarine warfare and the previous sinking of the Lusitania, created a strong push for military action. Consequently, on April 6, 1917, President Wilson declared war on Germany.
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