What changed dramatically during World War II, a shift neither understood nor appreciated by President Roosevelt and Secretary of State Cordell Hull, was the attitude of the American people. They were willing, as they had not been earlier, to assume their country's burden of responsibility in world affairs. Americans were guilty over their refusal to participate in the League of Nations. If only the most powerful nation in the world had thrown its weight behind a collective security system, the Holocaust and World War II might have been prevented. The war experience had been so painful and after 1945 the prospect of nuclear war so horrible that Americans were willing to make sacrifices in the form of economic aid for the rebuilding of Europe and to provide funds for defense against the looming threat of Soviet expansion. Reflecting these changed attitudes, Congress, on 21 September 1943, passed the Fulbright-Connally Resolution, which pledged U.S. participation in an international organization to keep the peace. Even before the passage of this measure, the leadership of the Republican Party had gathered on Mackinac Island, Michigan, to hammer out a position on the postwar order. Under the tutelage of Senator Arthur H. Vandenberg of Michigan and Governor Thomas E. Dewey of New York, the conferees devised a compromise resolution acceptable to most Republicans, which favored the formation of an international organization after the war.
The realization that positive measures would be needed to prevent a third world war convinced them that their leaders, regardless of party, must cooperate to best serve the national interests abroad. In order that the United States have a full and constructive impact on world events, Americans demanded that partisan politics be removed from foreign policy so that the United States could speak with a single voice in foreign affairs. Politicians, presidents, senators, and the members of the House of Representatives were to work to develop policies that would receive broad-based support.
Franklin D. Roosevelt, who was never fully committed to State Department planning for a postwar international organization, held a fuzzy conception of what the postwar world should look like. Roosevelt, however, did believe in cooperation among the great powers and summit diplomacy to maintain the peace. He was convinced that such cooperation had won the war and that major-power agreement would prevent another conflict. He never thought that the American people would support the stationing of U.S. troops abroad and the rebuilding of Western Europe. Moreover, to the president, bipartisanship meant total congressional acquiescence in the executive branch's conduct of foreign policy. In brief, he wanted to run foreign policy himself without congressional interference.
Into the breach stepped Senator Arthur Vandenberg. In an address to the Senate on 10 January 1945, marking another step in the establishment of bipartisan foreign policy, he rejected isolationism and pledged cooperation if the administration would state its plans for the postwar world with candor. Vandenberg announced that he would support the evolving United Nations. To further guarantee the peace and allay Russian distrust of the West, he called for a four-power military alliance to prevent another war and to ensure that Germany would not rearm. More important, he suggested maximum consultation and cooperation between the administration and the Senate in charting the course of American diplomacy in the postwar world.
The succession of Harry S. Truman to the presidency portended well for bipartisanship. Truman knew the senators as friends and had respect for their abilities. As a former member of the Senate establishment, he well understood the benefits of working closely with Senate and House committees, and as a new president, he needed all the support and advice he could garner. In the summer of 1945, the U.S. Senate ratified the charter of the United Nations by a vote of 89 to 2.