The United States' entry into World War I in 1917 significantly influenced the outcome of the conflict. Initially neutral, the U.S. was propelled into the war due to unrestricted submarine warfare by Germany and the interception of the Zimmermann Telegram, which proposed a military alliance between Germany and Mexico. U.S. forces, known as the American Expeditionary Forces (AEF), provided essential manpower and resources, aiding the beleaguered Allies in overcoming the Central Powers. Their involvement not only helped to tip the balance in favor of the Allies but also marked the United States' emergence as a world power and set the stage for its active role in global affairs thereafter.