The establishment of the United Nations is historically associated with Franklin D. Roosevelt, who was a prominent advocate during and after World War II. Roosevelt envisioned an international organization that would promote peace, security, and cooperation among nations to prevent future conflicts. His leadership during the war laid the groundwork for the UN’s founding charter, which was officially adopted in 1945. Roosevelt emphasized the importance of collective security, diplomacy, and human rights, elements central to the UN's mission today. His efforts were instrumental in shaping the post-war global order.