Which of the following factors contributed the most to the United States joining the Allied Forces during World War I?

Question

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Failure of the Schlieffen Plan

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Collapse of League of Nations

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Russia’s surrender to Central Powers

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Germany’s unrestricted submarine warfare

Answer 1

The factor that contributed the most to the United States joining the Allied Forces during World War I is:

Germany’s unrestricted submarine warfare.

This policy by Germany led to the sinking of civilian and neutral ships, including those with American passengers, which significantly increased anti-German sentiment in the U.S. and ultimately prompted America to enter the war on the side of the Allies.