Which factors led the United States to enter World War I in 1917?

• A. Unrestricted submarine warfare by Germany.
• B. The Zimmermann Telegram.
• C. Growing economic and ideological support for the Allies.
• D. All of the above.

Answer: (D)

To understand why the United States entered World War I in 1917, you have to see how several pressures lined up at that moment. Germany’s decision to resume unrestricted submarine warfare threatened American ships and lives and jeopardized neutral rights and trade, making staying out of the war increasingly difficult. Then the release of the Zimmermann Telegram—Germany’s proposal to Mexico to join a war against the United States—stoked fears of a broader conflict and swelled anti-German sentiment, pushing public opinion toward intervention. At the same time, the United States had deep economic and ideological ties to the Allies: it was lending large sums, trading heavily, and many Americans felt a moral obligation to support democracies and oppose autocratic powers. When these military, diplomatic, and economic pressures converged, entering the war in 1917 became the most coherent response.