On April 2, 1917, President Woodrow Wilson asked Congress to declare war on Germany, marking the United States entry into World War I. The decision came after Germanys unrestricted submarine warfare and the interception of the Zimmermann Telegram, which proposed a German-Mexican alliance. The U.S. mobilized its military and resources, which played a crucial role in tipping the balance in favor of the Allied Powers. Americas involvement in World War I shaped its future foreign policy and its position as a global power. The war ended in 1918, leading to major geopolitical changes.