Leading up to 1917 and the declaration of war against Germany , the labor unions , socialists , members of the Old Right , and pacifist groups in the United States publicly opposed participation , the obvious motive for the 1916 Preparedness Day Bombing stemming from this . When Woodrow Wilson ran for reelection in 1916 on the slogan " He Kept Us Out of War " , he received support from these groups ( although the Socialist Party of America ran its own candidate , Allan Benson ) . After Wilson was reelected , though , events quickly spiraled into war . The Zimmermann Telegram and resumption of unrestricted submarine warfare by Germany provoked outrage in the U.S. , and Congress declared war on April 6 . Conscription was introduced shortly thereafter , which the anti-war movement bitterly opposed . Many socialist , typified by Walter Lippmann , became enthusiastic supporters of the war . So too did Samuel Gompers and the great majority of organized labor unions . However , the IWW -- " Wobblies " — gained strength by opposing the war
Preparedness Day Bombing
Preparedness Day Bombing
Opposition to World War I