The United Nations came into existence in 1945, and the Republic of China was one of its founding members. The Republic of China once held a permanent seat in the Security Council. When the republic lost the mainland to the Chinese Communists in 1949, its government relocated to Taiwan. However, it continued claiming to be the sole legitimate government of all of China and held China’s seat at the UN. That changed in 1971 when the UN admitted the People's Republic of China and forced Taiwan out. Since then Taiwan has been barred from participating UN-related activities.
Although Taiwan no longer claims to be the legitimate government of China, Beijing continues to claim Taiwan as part of its territory. Taiwan’s efforts to rejoin the organization since the 1990s have been unsuccessful because of opposition from China, which holds veto power at the UN as one of the five permanent Security Council members.