Among isolationists in the interwar period there was fear of militarism. The historian Charles A. Beard felt the military interests seeking a larger navy would, if left to themselves, "extend America's 'strategic frontiers' to the moon." If Americans rejected the policy encouraged by Alfred Thayer Mahan, Theodore Roosevelt, John Hay, and Henry Cabot Lodge, and if by plan, will, and effort they provided "a high standard of life and security for the American people," using to the fullest the national resources, technical arts, and managerial skills in the United States, there would be no need for large military forces. Defense policy should be based on "security of life for the American people in their present geographical home"; the army and navy should not be huckstering and drumming agencies for profit seekers, promoters, and speculators or defenders of every dollar invested abroad. Guided by such a clarification of policy, Beard said, military authorities could make calculations adapted to clearly defined ends; until then they "will demand every gun and ship they can get." Beard saw military leaders committing themselves to a policy of trade promotion and defense all over the world. Sometimes, he believed, they took dangerous chances and then tried to convince the people that national interest or points of honor were at stake. As long as naval strategists demanded more ships, men, and financial support, by using "the kind of propaganda they have been employing," they were more a danger to American security than a guarantee of it.
Senators also frequently spoke out on these issues. Robert A. Taft also urged restraint on interventionist policies because he opposed war. He did not trust President Roosevelt; he thought there was little the United States could do about democracy abroad; and he felt war would expand the power of the federal government to the detriment of democracy at home. Not all isolationists would agree with this reasoning, especially since German and Japanese aims appeared more aggressive. Senator George Norris came to believe by the late 1930s that despite the dangers of militarism the United States must rearm.
The American Legion, an organization of veterans that emerged in the interwar period, also advocated programs of preparedness. The legion supported the idea of a naval disarmament conference in Washington in 1921–1922 but did not want to sacrifice an adequate navy for maintaining the position of the United States as a world power; nor did the legion want its support of the Kellogg-Briand Pact (1928) outlawing war as an instrument of national policy to imply any support for reduction in the nation's military establishment. Whether the American Legion has influenced public opinion or merely reflected it is uncertain. In the great foreign policy debate before Pearl Harbor, the organization had its own divisions on internationalism and isolationism; and, as for many Americans, the legion's general anticommunist stance gave way before the realities of World War II, returned with the Cold War, and adjusted to détente and the post–Cold War years. The size and organization of the American Legion have made it a more powerful lobby than its first antecedent, the Society of the Cincinnati; but it has also had public suspicion and criticism, reflecting perhaps the American civilian's distrust of military influence.
The first four decades of the twentieth century witnessed no marked trend toward militarism in the United States. But more than ever before in the nation's history, Americans were having to come to terms with world power, having to think about international relationships that had been far from their minds in earlier times. Many Americans believed that the old truths of civil-military relations were still valid, although they realized that some concessions were necessary for adequate defense in a world not free of war. The big question then and still today centers on how much is adequate. In the interwar years, the army was seldom above 200,000 men and most often below 150,000; there was rejection of conscription until 1940 and much debate on the advisability of compulsory Reserve Officers Training Corps in colleges. The navy also suffered postwar neglect, and many officers regretted naval weakness in the Pacific, where they considered Japan the enemy. A change came with Franklin D. Roosevelt's support of naval expansion and more jobs in the shipbuilding industry.