In what year did the U.S. enter World War I?

The United States entered World War I in 1917, a significant event that marked a turning point in the war. Prior to this, the U.S. had maintained a position of neutrality, despite increasing tensions and involvement through economic and military support to the Allies. The decision to join the conflict was influenced by several key factors, including unrestricted submarine warfare by Germany, which threatened American civilian lives and commercial interests, and the interception of the Zimmermann Telegram, in which Germany proposed a military alliance with Mexico against the United States.

By entering the war, the U.S. provided much-needed manpower and resources that bolstered the Allied forces, contributing to the eventual defeat of the Central Powers. The impact of the American entry into the war was profound, as it not only altered the dynamics of the conflict but also marked the U.S.'s emergence as a significant global power.