The arrival of the Cold War further weakened the traditional levers of congressional authority. The nature of the communist threat placed the government on close to a permanent war footing, while the advent of nuclear weapons provided an immediacy lacking in any previous challenge to U.S. national security. In this new situation, a constitutional theory emerged claiming that the commander-in-chief clause bestowed an independent foreign policy power upon the executive, an argument almost never previously advanced. On the domestic front, the perceived lessons of the late 1930s bolstered the Truman administration's strategy of equating its own foreign policy principles with the concept of bipartisanship. A century and a half before, Jefferson had shown how aggressive presidential leadership and partisan unity could work to diminish congressional authority. Now, Harry Truman looked to create a party unity between executive and legislature that did not exist, with the aim of stifling congressional dissent. Faced with a Congress controlled by Republicans between 1947 and 1949, the president essentially regarded congressional attacks not as legitimate institutional challenges but as nothing more than partisanship.
Not surprisingly, then, the early Cold War is not remembered as a period of intense congressional activism in the international arena. As Arthur Vandenberg conceded during his stint as Senate Foreign Relations Committee chair in the Eightieth Congress, issues seemed to reach Capitol Hill only when they had developed to a point where congressional discretion was badly restricted. Indeed, what Truman's final secretary of state, Dean Acheson, dubbed the "Vandenberg treatment"—granting to the Michigan senator small, superficial concessions and a dose of public praise—aptly describes the common view of the congressional role in Truman's foreign policy.
In many ways, congressional power did diminish in the early stages of the Cold War, although this was partly because—as with the Reciprocal Trade Agreements Act fifteen years earlier—the legislature willingly surrendered its role. At times the body seemed eager to expand the president's foreign policy powers beyond even what Truman desired. Such sentiments explain the overwhelming approval of initiatives such as the National Security Act (1947), the North Atlantic Treaty Organization (1949), and the post-1950 expansion of the defense budget. They also affected the early congressional response to the Korean War; at the time, several senior members expressly asked Truman not to involve Congress in the decision. With the combination of NSC 68—the document that deemed the triumph of communism anywhere in the world a threat to U.S. national security—and the onset of the Korean War dramatically escalating the military budget, the beneficiaries of defense spending spread around the country. As a result, members of Congress who even considered opposing defense appropriations were vulnerable to the charge that they were not only subverting national security but also failing to protect the economic interests of their constituents. In the decade between the end of the Korean War and the end of John F. Kennedy's presidency, defense bills passed with an average of less than one negative vote in both chambers.
Until the Korean War began, however, the congressional response to the Cold War was considerably more complex. In 1947, even as the administration was uniting behind George Kennan's containment doctrine, Congress seriously considered three alternative approaches to world affairs. A small group of Democratic liberals supplied the most tenacious opposition to the Truman Doctrine, in which the president pledged to assist any government threatened by communist takeover. Led by Claude Pepper and Edwin Johnson, they charged that extending military assistance to undemocratic regimes in Greece and Turkey would contradict the internationalist ideals for which the United States fought World War II. To the administration's right, a sizable bloc of Republicans led by Senator William Knowland of California and Representative Walter Judd of Minnesota demanded that the administration reorient its foreign policy toward East Asia by aiding the Nationalists in China's civil war. Finally, nationalists ranging from the talented (Robert Taft of Ohio) to the unscrupulous (Pat McCarran of Nevada) questioned any initiative that would threaten U.S. sovereignty and argued that an activist foreign policy would dangerously strengthen the federal government. They instead advocated waging the Cold War through domestic measures that would crack down on communist sympathizers. This point of view enjoyed strong support in the House of Representatives, which was more subject to conservative pressures generated by the 1946 elections.