World War I

World War I, lasting from 1914 to 1918, involved many nations, but the U.S. joined the conflict in 1917. Initially neutral, the U.S. was drawn in by unrestricted submarine warfare and the Zimmermann Telegram, which revealed German plans to ally with Mexico against the U.S. American troops helped tip the balance in favor of the Allies, leading to victory. The war significantly impacted U.S. society and economy, promoting a stronger international presence and sparking debates over nationalism and isolationism. Post-war, the Treaty of Versailles aimed to prevent future conflicts but also sowed the seeds for World War II.