The armistice of November 11, 1918, ended the fighting in World War I. In 1919, delegates drafted the Treaty of Versailles. A critical part of the treaty was the establishment of the League of Nations, which some members of Congress opposed based on the deep isolationist sentiment among many Americans. Although President Wilson campaigned aggressively for U.S. participation, the U.S. Senate did not consent to ratify the treaty. Not until 1945, with the creation of the United Nations after World War II, did the United States join an international organization to promote cooperation and peaceful resolutions of conflict.