In proclaiming goals whose achievements always eluded the possibilities of his prescriptions, Wilson laid the foundation for a pervading postwar isolationism. For countless Americans, nothing in the country's recent experience dictated the necessity of a permanent, continuous American involvement in European politics.
For other Americans, often intellectuals and academicians, Wilson's vision of a new world order, free of all reliance on force, was too essential for the world's welfare to be discarded in deference to isolationism. Inasmuch as both groups were antagonistic to the conservative tradition of American diplomacy, there was little to separate idealists from realists in the national debate. Isolationism insisted that the nation had no external interests that merited the use of force, that events outside the hemisphere were inconsequential.
In apparent contrast, internationalism declared that U.S. interests existed wherever governments challenged peace or human rights. It insisted not only that they mattered but also that the universal acceptance of democratically inspired principles of peaceful change would control them. Every program fostered by American internationalists during the two postwar decades—membership in the League of Nations and the World Court, the employment of arbitration conventions, the resort to consultation in the event of crises, collective security, naval disarmament, or the outlawry of war—denied the need of any precise definition of ends and means in American foreign policy. The burgeoning fields of diplomatic history and international law rested on Wilsonian principles. Under the presumptions of a controlling public opinion and a common interest in peace, international lawyers joined national leaders in rationalizing inaction in the face of growing threats. Notions of collective security served as a device of the status quo powers to prevent change in the international system. The Western preference for the status quo, in the absence of any program to change it peacefully, never recommended the means for preserving it beyond the acceptance of war.
Whatever remained of the realist-idealist cleavage in American thought and action was again clouded by the almost universal national acceptance of U.S. involvement in World War II. Realists presumed that the war, like the Great War of 1914, would, with the defeat of the Axis, reaffirm Europe's traditional balance of power and reestablish the essential elements of the Versailles settlement of 1919. To that end, Winston Churchill and Franklin D. Roosevelt, in the Atlantic Charter of August 1941, advocated the return of East-Central Europe to its prewar status. American idealism, however, assigned the war a deeper, largely humanitarian purpose. In his lend-lease proposal of January 1941, Roosevelt adopted the goal of the Four Freedoms—freedom of speech, freedom of worship, freedom from want, and freedom from fear—in his crusade against the Axis powers. In his book Price of a Free World (1942), Secretary of Agriculture Henry Wallace proposed, as the war's true purpose, not only the elimination of fascism from the world, but also the establishment of freedom for all peoples, the final triumph of democracy, and the elimination of poverty and hunger everywhere. At the Casablanca Conference of January 1943, Roosevelt announced his goal of unconditional surrender to eliminate any German, Italian, or Japanese influence from the postwar treaty-making process—essential for the construction of the perfect peace. Unfortunately, such idealist presumptions failed to anticipate the Soviet Union's overwhelming contribution to the allied victory and the demands that the Kremlin would make on any postwar settlement.