A majority of Americans came to accept Roosevelt's policy of gradually increasing both aid to the Allies and military preparation at home. When war erupted most people were still unaware that the free security from which they had unknowingly benefited for so long was gone forever. Many Americans believed that when the war was over national life would return to the prewar style. As Samuel A. Stouffer and others note in their sociopsychological study The American Soldier (1949), there was little feeling of personal commitment to war after the early sense of national peril had disappeared. The war was simply a detour that must be taken before one could return to the main, or civilian, road. At war's end the soldier had no desire to reform the United States or the world; he was interested in himself and his family. Cessation of hostilities brought not-surprising demands for rapid release of fathers, sons, and husbands; by 1946 the number of men on active duty had fallen from over 12 million to little more than 3 million, which was reduced by half the following year. In his plans for the postwar world, Roosevelt had sensed the public mood and anticipated a small armed force. At Tehran, when Stalin suggested that Roosevelt's idea of four policemen to preserve world peace might require sending U.S. troops to Europe, Roosevelt envisaged the United States providing ships and planes while Britain and the Soviet Union provided the land armies. And at Yalta the president doubted if U.S support for future peace would include "maintenance of an appreciable American force in Europe." Clearly, the United States accepted an international role and would not make the mistake of rejecting membership in the new world organization, but Americans expected to fit their participation into a familiar mold requiring only limited military effort. This paralleled Wilson's first hopes in 1917 that the American contribution to the war would come mainly from the navy and industrial production, and Roosevelt's hopes in 1940 and 1941 that nonbelligerency would prevent defeat of Germany's enemies while keeping the United States out of war. These hopes were lost in events.
Although most Americans during and immediately after the war thought mainly of returning to peacetime pursuits with little or no consideration of America's role in the world and what that role might require, there were military leaders pondering the country's future and how to protect its interests. Even shortly before the Pearl Harbor attack, as noted by Michael S. Sherry in his Preparing for the Next War, General George Marshall was thinking about peace after the imminent war and the war to follow it. Despite this slight beginning, postwar planning did not become serious for more than a year, and even then the planners had to deal with many uncertainties including vaguely expressed plans from political leaders and lack of cooperation inherent in the rivalries among the army, navy, and virtually autonomous army air force. All aspired to a preeminent place in defending national interests perhaps challenged by Soviet expansion, a concern of the Joint Chiefs of Staff since 1942. Planning proposals that emerged included universal military training, unification of the services, and an independent and large air force, but unanimity was lacking except on the essential ability for rapid mobilization. A proposal for universal military training eventually received President Harry Truman's support but never passed Congress. The country relied on the draft until 1973 with a brief hiatus in 1947–1948. The National Security Act of 1947 provided for coordination of the armed services and an independent air force. Although the war ended without planning consensus, hurried efforts in the latter half of 1945 brought recommendations advocating a policy of deterrence and preventive war. Sherry points out that such recommendations contrasted with earlier practice—going from a passive to an active defense. There followed military budgets lower than those of wartime but higher than prewar levels and continued large research-and-development funding, allowing soldiers and scientists to remain partners. All of this, Sherry believes, created an ideology of preparedness and Cold War mentality permitting militarist influence to permeate American society.