When did the United States officially enter World War I?

The United States officially entered World War I on April 6, 1917. This decision came after a series of events that increased tensions between the U.S. and Germany, including unrestricted submarine warfare and the interception of the Zimmermann Telegram, which proposed a military alliance between Germany and Mexico against the United States. The U.S. entry into the war significantly bolstered the Allied powers and shifted the momentum of the conflict.

Prior to this, in 1915 and 1916, while the U.S. was involved in diplomatic efforts and debates about entering the war, it had not yet committed troops or declared war. By 1918, the war was nearing its end with the signing of the armistice on November 11, but the definitive entry point for the U.S. was in 1917, making this year a crucial turning point in both U.S. history and the overall outcome of World War I.