Roosevelt had been a strong supporter of the League of Nations back in 1919-20 , but was determined to avoid the mistakes Woodrow Wilson had made . The United Nations was FDR 's highest postwar priority . He insisted on full coordination with the Republican leadership . He made sure that leading Republicans were on board , especially Senators Arthur Vandenberg of Michigan , and Warren Austin of Vermont . . In a broad sense , Roosevelt believed that the UN could solve the minor problems and provide the chief mechanism to resolve any major Issues that arose among the great powers , all of whom had a veto . For FDR creating the UN was the most important goal for the entire war effort . For FDR , " establishing the United nations organization was the overarching strategic goal , the absolute first priority . " Roosevelt was especially interested in international protection of human right , and in this area his wife played a major role as well . The Allies had agreed to the basic structure of the new body at the Dumbarton Oaks Conference in 1944 . At Yalta , Roosevelt , Churchill , and Stalin agreed to the establishment of the United Nations , as well as the structure of the United Nations Security Council . Stalin insisted on having a veto and FDR finally agreed . The participants at Yalta also agreed that the United Nations would convene for the first time in San Francisco in April 1945 in the United Nations Conference on International Organization . Roosevelt considered the United Nations to be his most important legacy . He provided continuous backstage political support at home and with Churchill and Stalin abroad . The Big Four of the United States , Britain , Soviet Union and China would make the major decisions , with France added later to provide permanent members of the all-powerful Security Council . Each had a veto power , thus avoiding the fatal weakness of the League of Nations , which had theoretically been able to order its members to act in defiance of their own parliaments . Roosevelt went public with strong advocacy in the 1944 presidential campaign , and turned detailed planning over to the State Department , where Sumner Welles and Secretary Cordell Hull worked on the project . It was his ideas that " four policemen " would collaborate to keep and enforce the peace . The United States , Britain , Soviet Union and China made the major decisions and became permanent members of the all-powerful Security Council ; France was added to make five policemen . Stalin insisted on a veto power . Roosevelt finally agreed , thus avoiding the fatal weakness of the League of Nations , which theoretically could order its members to act in defiance of their own parliaments . From 21 September to 7 October 1944 , representatives of the Republic of China , Britain , the US and the USSR met to elaborate plans at the Dumbarton Oaks Conference in Washington , D.C. Those and later talks produced proposals outlining the purposes of the United Nations organization , its membership and organs , as well as arrangements to maintain international peace and security and international economic and social cooperation . Governments and private citizens worldwide discussed and debated these proposals . Winston Churchill urged Roosevelt to restore France to its status of a major Power after the liberation of Paris in August 1944 . At the Yalta Conference it was agreed that membership would be open to nations that had joined the Allies by 1 March 1945 . Brazil , Syria and a number of other countries qualified for membership by declarations of war on either Germany or Japan in the first three months of 1945 – in some cases retroactively
United Nations Conference on International Organization
United Nations Conference on International Organization
History of the United Nations