Number of League of Nations and UN member states by year, 1920-2022

In the aftermath of the First World War, the League of Nations was established at the Paris Peace Conference of June 28, 1919, and the Covenant of the League of Nations made up Part I of the Treaty of Versailles. The League came into being on January 10, 1920, with the primary objective of preventing further global conflicts by maintaining international peace and security through diplomacy and negotiation rather than military action, as well as a focus on the protection of human rights and international disarmament. Unfortunately for the League, the U.S. Congress refused to join (despite President Wilson being the leading architect behind the League's founding), while the other Great Powers (Britain, France, Italy, and Japan) were reluctant to provide military assistance or adhere to economic sanctions put in place by the League. By the end of 1934, League membership reached its highest level of 58 member states; however, this was the year after the two primary aggressors of the Second World War, Germany and Japan, had left the League. Over the next decade, the rise of nationalism and the impact of the Second World War saw the inevitable collapse of the League of Nations, and its official dissolution in 1946.

Development of the United Nations

The League of Nations was replaced by the United Nations (UN) following the Second World War. The UN came into being in June 1945, when 50* governments met in San Francisco to draft the original UN Charter, which came into effect on October 24, 1945. Since its founding, there have been approximately 200 different member states of the United Nations, with some (such as Yugoslavia or East Germany) no longer existing, while others have been renamed or their borders have been redefined. The largest increases in membership came in the 1950s as many European colonies (mostly in Africa and Asia) gained independence, and again in the early 1990s, with the fall of the Soviet Union and communism in Eastern Europe. The latest member state to join the UN was South Sudan in 2011.

International relations in the UN's early history were strained, as tensions caused by the Cold War impeded the UN's ability to act effectively, but since the Soviet Union's dissolution in 1991 the UN has been able to expand and diversify its peacekeeping efforts with fewer obstacles. The six principal organizations of the UN are the General Assembly, the Security Council, the Economic and Social Council, the Trusteeship Council, the International Court of Justice and the UN Secretariat. The highest-ranking official in the UN is Secretary General António Guterres, who is the former Prime Minister of Portugal. The UN is headquartered in New York, and has three regional headquarters in Geneva, Nairobi, and Vienna (and the International Court of Justice is based in The Hague, Netherlands).

Non-member states of the UN

Along with the 193 member states of the UN, there are two countries or territories with permanent observer status. The first of these is the Holy See (Vatican City), which is the only fully independent country in the world that is not a member state. However, it has full access to the UN's resources, but abstains from the voting process due to the Pope's preference not to get involved in geopolitical affairs. Palestine is the other state with this status, as the UN favors Palestine becoming a fully independent nation, but will not acknowledge this claim until Palestine's conflict with the UN member state Israel has been peacefully resolved. Since the 2023 Israeli invasion of Gaza, calls for Palestinian membership have grown, particularly from within the UN and its many organizations that have played an integral role in Gaza's daily operations since the 1950s.

Of the other six states without non-member observer status, Kosovo's independence from Serbia has the most international support, and it is currently recognized by over 100 member states. The Republic of China (Taiwan) held China's seat in the UN from it's founding until 1971, where it was then transferred to the People's Republic of China (China). Since then, Taiwan has been represented at the UN by the Chinese government (who is one of the five permanent members of the UN Security Council), and only 13 member states recognize Taiwan's independence. As of 2024, Indonesia remains the only country to have ever withdrawn its UN membership, in 1965, although this was reinstated the following year.