The United Nations (UN) is an intergovernmental organization created in 1945 to promote world peace and international cooperation. It was established after World War II to replace the ineffective League of Nations and prevent future conflicts. The UN now has 193 member states and carries out its missions through subsidiary organizations. Its New York City headquarters resides in international territory, with other main offices in Geneva, Nairobi, and Vienna. The UN was initiated by U.S. President Franklin D. Roosevelt and its charter took effect in 1945, though its peacekeeping role was complicated by the Cold War.