Historian Edward T. O’Donnell explores America’s dramatic shift from neutrality to engagement in World War I, highlighting the war’s overlooked but profound impact. He examines the causes of the conflict, American isolationism, and the pivotal events that led to U.S. involvement. O’Donnell also discusses military mobilization, the nation’s role in defeating the Central Powers, and the domestic consequences, including propaganda, suppression of dissent, and Wilson’s promotion of the League of Nations.