This ambiguity dissipated after the European phase of World War II began in September 1939, ushering in what eventually became the most internationalist phase of American foreign policy. Between 1939 and the attack on Pearl Harbor, the country was sharply divided between internationalist advocates of aid to America's European allies and isolationists who feared such aid would lead to an unwanted and unnecessary American involvement in the war. The internationalists were themselves divided between outright interventionists and those who, led by William Allen White and his Committee to Defend America by Aiding the Allies, argued that sending military equipment and loans would make American participation in the war against Adolf Hitler unnecessary. All these internationalists called for the repeal or modification of neutrality legislation and other laws that hindered the free flow of materials to governments fighting the Axis Powers. By late 1941, Washington had lifted most restrictions against sending aid to Great Britain. Rejecting the charge of inconsistency, these same internationalists applauded the imposition of economic sanctions against Japan regarding oil and scrap iron.
The European war in 1939 and the attack on Pearl Harbor in 1941 seemed to confirm what internationalists had been saying for years about the need for an effective collective security organization. They also reinforced the argument in favor of American membership. Isolation, charged the internationalists, had not only failed but made world wars more rather than less likely. Even months before Pearl Harbor, 87 percent of Americans claimed they favored some kind of postwar organization. To most Americans, Hitler had made internationalism not only respectable but necessary.
The president of the League of Nations Association, James T. Shotwell, and his executive director, Clark M. Eichelberger, founded the somewhat pompously named Commission to Study the Organization of Peace, which cooperated with the State Department in formulating U.S. proposals for what eventually became the United Nations. (The League of Nations Association changed its name to the American Association for the United Nations in 1943.) Next in importance to the commission was the Federal Council of Churches to Study the Basis of a Just and Durable Peace, led by collective-security advocate and future secretary of state John Foster Dulles. Altogether, thirty-six private internationalist organizations joined this effort to create the UN, threatening to make the task chaotic.
The task of coordinating the planning for the UN fell mainly on an obscure State Department economist, Leo Pasvolsky, who headed the department's Division of Special Research (which had, at various times, other bland titles). No one worked more tirelessly or anonymously than he. At a time when American planning for the UN was hampered by rivalries between State Department officers, between Republicans and Democrats, and between congressional leaders and State Department officials, Pasvolsky managed to keep the project afloat. And because American officials had done much more planning than their counterparts in other countries, the final charter would reflect American thinking to a great extent.
The UN Charter was drafted primarily at three conferences: Dumbarton Oaks (August–October 1944), Yalta (February 1945), and the special UN conference at San Francisco (April to June 1945). Although the president had raised the issue of a postwar organization with the USSR's Joseph Stalin and Britain's Winston Churchill at various wartime conferences, the details—including the critical questions relating to membership and great power authority—were postponed until the latter stages of the war. A small group of officials, not the internationalist movement generally, resolved these matters, agreeing with Stalin's insistence that each of the great powers possess a permanent veto in the UN's Security Council. They also agreed that the Security Council, and not the larger General Assembly, would control the UN's enforcement machinery.
This time the president and his advisers, in contrast to President Wilson, did their political homework. They employed a broad spectrum of American internationalists to prepare the way for ratification of the UN Charter. Preceding the vote the administration launched the most ambitious campaign to support a foreign policy objective of the entire twentieth century. It included parades, parties, lectures, and radio and school programs. UN supporters turned isolationism into a dirty word. Everyone, it seemed, had become an internationalist, which masked the real differences within the movement. Even many Republicans who had opposed League of Nations membership a quarter of a century earlier now promoted UN membership. Less than a month after the San Francisco Conference, the Senate ratified the UN Charter by 89 to 2.
The charter reflected much of the structure and many of the operational features of the League Covenant, including a basic reliance upon power politics and a response to crises only after a breach of the peace. Like Woodrow Wilson, Franklin Roosevelt believed that an alliance of nations, functioning through an organization, could best maintain stability (though Wilson thought more in terms of universality, Roosevelt more in terms of great power cooperation). The United Nations Charter called for states to sacrifice very little sovereignty. Even former American isolationists could call themselves internationalists, knowing that American interests were protected by the permanent veto.