Prior to the Japanese attack on Pearl Harbor, Lewis was staunchly opposed to American entry into World War II. Initially, he tapped into the anti-militarism that animated the left wing of the CIO. He publicly opposed the prospect of a peacetime draft as "associated with fascism, totalitarianism and the breakdown of civil liberties," claiming in his 1940 Labor Day speech that there was "something sinister about the attempt to force conscription upon our nation, with no revelation of the purposes for which conscription is sought." Lewis' opposition to American intervention continued after the leftist coalition against it had splintered. In August of 1941 he joined Herbert Hoover, Alfred Landon, Charles Dawes, and other prominent conservatives in their appeal to Congress to halt President Roosevelt's "step-by-step projection of the United States into undeclared war." This action earned him the enmity of those on the left, including Lee Pressman and Len De Caux.