Top Photo: The United Nations Fight for Freedom – United States Office of War Information, poster by Leslie Ragan. National Archives

On the afternoon of April 16, 1945, just four days after the death of Franklin D. Roosevelt, President Harry S. Truman delivered an address to the nation before a joint session of Congress. He called upon Americans to remember their president of more than 12 years and to honor his legacy by pushing on to total victory over the Axis powers in World War II. But Truman also reminded Americans that defeating Germany and Japan was not enough—the United States also had to lead the way in building a better world, a world where destructive wars and mass atrocities could be stopped in their tracks. He pledged that Americans “will face the problems of peace with the same courage that we have faced and mastered the problems of war.” 1 

Just over a week later, on the other side of the country in San Francisco, California, a conference to establish a new international organization to replace the League of Nations was scheduled to begin. In his April 16 speech, Truman acknowledged that building a new international organization was a difficult task, but warned that, “without such [an] organization, the rights of man on earth cannot be protected. Machinery for the just settlement of international differences must be found. Without such machinery, the entire world will have to remain an armed camp. The world will be doomed to deadly conflict, devoid of hope for real peace.”2

Failures of the League of Nations

The failure of the League of Nations contributed to the outbreak of World War II. Established by the victorious Allied powers at the end of World War I (1914–18) to forestall another destructive conflict, the League of Nations’ goals were ambitious: according to its founding covenant, the League’s role was “to promote international co-operation and to achieve international peace and security” by obliging its members to avoid war, by fostering “just and honorable relations between nations,” by firmly establishing international law as the basis for international relations, and by respecting justice and all treaty obligations between organized peoples. 3  But despite its lofty goals, the institution was deeply flawed from the start.

For such an organization to succeed, it needed the support of the world’s major powers, and from the beginning, the League of Nations did not have it. US President Woodrow Wilson had been a strong supporter of the League of Nations. When he outlined his “Fourteen Points” for achieving a peaceful world in a January 8, 1918, speech to Congress, he called for the creation of “a general association of nations,” which was necessary “for the purpose of affording mutual guarantees of political independence and territorial integrity to great and small States alike.”4  But after thousands of American soldiers died far from home during World War I, many Americans were uninterested in further expanding the United States’ role in the world, and despite Wilson’s best efforts, the Senate rejected US membership in the League. Another major power, the newly formed Soviet Union, which was in the midst of a civil war in the years after World War I, did not join the League of Nations until 1934, more than a decade after its founding.

Furthermore, structural weaknesses hindered the League’s ability to enforce peace on its member states. Without coercive powers of its own, and with no means to compel member states to use their militaries on its behalf, there was little the League of Nations could do to punish anyone who defied it. As historian Zara Steiner wrote, “Its weaknesses arose from the attempt to restrict the behavior of member states which, by their very definition, acknowledged no superior secular authority.”5  

During the 1930s, the League repeatedly failed to stop Italy, Germany, and Japan from expansionist activity, and all three powers eventually left the League altogether. Although the League of Nations did not hold its final session until April 18, 1946, the institution that began with such hope essentially ceased to matter in international relations once World War II commenced.

Origins of the United Nations in World War II

After the United States entered World War II in late 1941, leaders of the anti-Axis alliance began referring to themselves as the “United Nations.” At the end of their first major summit in Tehran, Iran, in late 1943, Roosevelt joined with fellow Allied leaders Winston Churchill of the United Kingdom and Joseph Stalin of the Soviet Union to issue a declaration on their common objectives. In addition to defeating Germany and Japan, the leaders of these three United Nations reaffirmed their great responsibility to “to make a peace which will command the good will of the overwhelming mass of the peoples of the world, and banish the scourge and terror of war for many generations.”6  

In a private meeting with Stalin during the Tehran Conference, Roosevelt outlined a plan to create several international organizations to replace the League of Nations, plans that addressed the League’s failures. One of these organizations, which the American president referred to as “The Four Policemen,” was to be made up of the United States, the Soviet Union, Great Britain, and China. This body “would have the power to deal immediately with any threat to the peace and any sudden emergency which requires this action.”7  While this proposal had the advantage of addressing the League of Nations’ fatal flaw of having no effective enforcement powers, it raised the difficult question of who would have the most power and influence in the new international organization.

The United Nations fight for freedom. Poster depicts an etching of the Statue of Liberty on a black background on the left side of the poster. The flags of the wartime "big four" are in the top row, while the others are listed in alphabetical order below. On the right there are pictures of flags of 30 countries. Poster has black background with white text at the top of the page and a white border all around. U.S. Government Printing Office: 1942-O-498304.

Important discussions about the makeup of an international organization to replace the League of Nations took place from August 21 to October 7, 1944, at an estate in the Georgetown neighborhood of Washington, D.C., called Dumbarton Oaks. Two days after the conference concluded, US officials released a report outlining a “general international organization.” Its goals would be to “maintain international peace and security,” to “develop friendly relations among nations,” to “achieve international cooperation in the solution of international economic, social and other humanitarian problems,” and to “afford a center for harmonizing the actions of nations in the achievement of these common ends.”8  The final outline roughly resembled the plan Roosevelt presented to Stalin at the Tehran Conference less than a year before. The new organization, which would be “open to all peace-loving states,” would have several major organs, including a general assembly composed of all member states and a security council, which would include representatives from the major Allied nations—the United States, the Soviet Union, the United Kingdom, China, and France.

As World War II entered its final months, some prominent Americans were changing their view of American involvement in international affairs. One of the most significant of these figures was Senator Arthur H. Vandenberg, a Republican from Michigan who before the Japanese attack on Pearl Harbor had strongly opposed US intervention in World War II. Addressing Roosevelt in a speech to the Senate on January 10, 1945, he argued that the attack on Pearl Harbor had dramatically altered his views of the United States’ role in the world. Breaking with his past anti-interventionist views, he told the president and his fellow senators that “our oceans have ceased to be moats which automatically protect our ramparts.”9  A few months later, Vandenberg would travel to San Francisco as part of a bipartisan delegation to shape the successor to the League of Nations: the United Nations.

Allied leaders reiterated their calls for a new international organization, which would take on the official name of their alliance, the United Nations, at the Yalta Conference of February 1945. Present at the meeting were the leaders of the three major Allied powers: Roosevelt, Churchill, and Stalin. In a communiqué released at the end of the conference, the three Allied leaders “resolved upon the earliest possible establishment with our allies of a general international organization to maintain peace and security. We believe that this is essential, both to prevent aggression and to remove the political, economic and social causes of war through the close and continuing collaboration of all peace-loving peoples.” 10 The so-called “Big Three” further pledged to call a conference in San Francisco two months later on April 25 to draw up a charter for the new organization.

The San Francisco conference lasted for two months and saw fierce debates over the makeup of the proposed international organization. Delegates argued fiercely over a range of issues, including the makeup of the powerful Security Council and the powers granted to its member states. Despite their shared victory over Nazi Germany, rising tensions between the United States and the Soviet Union complicated these negotiations as American and Soviet officials increasingly distrusted the other government’s motives in setting up the new world body.

At 10:53 p.m. on June 25, 1945, after much debate and compromise, the delegates voted unanimously to approve the new United Nations charter. As The New York Times reported the following day, the crowd of more than 3,000 people in the War Memorial Opera House “jumped to its feet to cheer and applaud for a full minute.”11

Conclusion

The United States’ decision to join the United Nations was a departure from its isolationist past. Unlike the aftermath of World War I, when America refused to join the League of Nations, the emerging superpower opted to join the new UN, and to this day, its headquarters remain in New York City. It was, in the words of historian Robert Divine, a “second chance” for Americans to fully embrace their role in the world in the wake of World War II. 12

In the 80 years since its creation, the United Nations has played a key role in international affairs, from providing relief aid to disaster areas and conflict zones to protecting cultural heritage sites around the world. Like the League of Nations, the UN has also worked to bring global conflicts to an end, and while it has not always succeeded, it has long outlasted its predecessor. 

• 1

  Harry S. Truman, “Address Before a Joint Session of Congress,” April 16, 1945, The American Presidency Project (URL: https://www.presidency.ucsb.edu/documents/address-before-joint-session-the-congress). Accessed 6/25/2025. 

• 2

  Truman, “Address Before a Joint Session of Congress,” April 16, 1945, The American Presidency Project (URL: https://www.presidency.ucsb.edu/documents/address-before-joint-session-the-congress). Accessed 6/25/2025.

• 3

  “The Covenant of the League of Nations,” The Avalon Project: Documents in Law, History and Diplomacy (URL: https://avalon.law.yale.edu/20th_century/leagcov.asp). Accessed 6/25/2025. 

• 4

  “President Woodrow Wilson's 14 Points (1918),” “Milestone Documents,” National Archives. (URL: https://www.archives.gov/milestone-documents/president-woodrow-wilsons-14-points#transcript). Accessed 6/25/2025. 

• 5

  Zara Steiner, The Lights That Failed: European International History, 1919-1933 (Oxford, UK: Oxford University Press, 2005), 40. 

• 6

  Agreed text of the “Declaration of the Three Powers,” December 4, 1943, Foreign Relations of the United States (FRUS): Diplomatic Papers, The Conferences at Cairo and Tehran, 1943 (Washington, D.C.: U.S. Government Printing Office, 1961). (URL: https://history.state.gov/historicaldocuments/frus1943CairoTehran/d411). Accessed 6/29/2025. 

• 7

  Bohlen Minutes of a conversation between Roosevelt and Stalin, November 29, 1943, FRUS: Diplomatic Papers, The Conferences at Cairo and Tehran, 1943 (Washington, D.C.: U.S. Government Printing Office, 1961). (URL: https://history.state.gov/historicaldocuments/frus1943CairoTehran/d365). Accessed 6/29/2025. 

• 8

  Annex to Press Release Issued by the Department of State, October 9, 1944, FRUS: Diplomatic Papers, 1944, General, Volume I (Washington, D.C.: U.S. Government Printing Office, 1966). (URL: https://history.state.gov/historicaldocuments/frus1944v01/d506). Accessed 6/25/2025. 

• 9

  Vandenberg, “American Foreign Policy,” January 10, 1945, “Classic Senate Speeches,” United States Senate. (URL: https://www.senate.gov/artandhistory/history/common/generic/Speeches_Vandenberg.htm). Accessed 6/25/2025.

• 10

  “No. 1417: Communiqué at the End of the Yalta Conference,” FRUS:Diplomatic Papers, The Conference of Berlin (The Potsdam Conference), 1945, Volume II (Washington, D.C.: U.S. Government Printing Office, 1960) (URL: https://history.state.gov/historicaldocuments/frus1945Berlinv02/d1417). Accessed 6/25/2025. 

• 11

  Lawrence E. Davies, “Historic Plenary Session Approves World Charter,” The New York Times, June 26, 1945. 

• 12

  Robert A. Divine, Second Chance: The Triumph of Internationalism in America During World War II (New York: Atheneum, 1967).