The United States' involvement in World War I was driven by several key factors:
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Unrestricted Submarine Warfare: One of the most immediate reasons was Germany's policy of unrestricted submarine warfare, which included the sinking of civilian and commercial ships without warning. The sinking of the British ocean liner RMS Lusitania in 1915, which resulted in the deaths of 128 Americans, heightened tensions and public outrage in the U.S.
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Economic Interests: The U.S. had significant economic ties to the Allies, particularly Britain and France. American banks and businesses had extended loans and sold arms and supplies to these countries. A victory for the Central Powers could jeopardize these investments and lead to significant financial losses.
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Propaganda and Public Opinion: British propaganda was effective in shaping American public opinion against Germany, portraying the Allies as fighting for democracy and civilization against German militarism. The narrative influenced many Americans to support the Allies.
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The Zimmermann Telegram: In early 1917, British intelligence intercepted and revealed a secret telegram from German Foreign Minister Arthur Zimmermann to Mexico, proposing a military alliance between Germany and Mexico in the event the U.S. entered the war. This pushed public opinion further against Germany and increased calls for U.S. intervention.
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Ideological Factors: President Woodrow Wilson framed the U.S. entry into the war as a fight for democracy. He believed that the war offered an opportunity to promote democratic ideals and prevent future conflicts through international cooperation.
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Global Balance of Power: The U.S. was increasingly concerned about maintaining a balance of power in Europe. A Central Powers victory could destabilize Europe and affect U.S. interests internationally.
These factors combined to lead President Wilson to ask Congress for a declaration of war against Germany on April 2, 1917, marking the official entry of the United States into World War I.