April 1917Reputable sourceWell documented
The United States Enters World War I
On the timeline · around April 1917 ·
What happened
After German submarines resumed unrestricted attacks on shipping and the intercepted Zimmermann Telegram revealed a German bid to ally with Mexico, the United States declared war in April 1917. Some two million American troops helped tip the balance on the Western Front before the armistice of November 1918.
Why it matters
World War I ended a century of American avoidance of European wars, and President Wilson's push for a League of Nations — rejected by the Senate — foreshadowed the country's later role as a global leader.
Sources
Related timelines
- World War I → — The Great War