The United Nations was an international organisation created in the aftermath of the Second World War to provide a framework for cooperation between states and to help maintain international peace and security. Its Charter was drafted at the United Nations Conference on International Organization in San Francisco between 25 April and 26 June 1945. Fifty countries participated in the conference, and the resulting Charter established the organisation.
The United Nations formally came into existence on 24 October 1945 after the Charter had been ratified by the required major powers and other signatories. It replaced the earlier League of Nations as the principal global organisation concerned with international cooperation, although its structure and powers were different.
The United Nations has several principal organs through which its work is conducted. The General Assembly provides a forum in which member states debate international issues and adopt resolutions. The Security Council has primary responsibility within the UN system for international peace and security and includes five permanent members with veto powers, together with elected non permanent members. The International Court of Justice deals with disputes between states and provides advisory opinions on legal questions. The Economic and Social Council coordinates work relating to economic and social matters, while the Secretariat carries out administrative and operational functions under the Secretary General. The Trusteeship Council became inactive after the completion of the UN trusteeship system.
The UN system also includes numerous specialised agencies, programmes and related organisations working in areas such as health, education, food, refugees, development, aviation, labour and communications. Examples include the World Health Organization, UNESCO, the Food and Agriculture Organization and the International Labour Organization, although these organisations have different legal relationships with the United Nations. UN agencies and programmes therefore do not constitute one single administrative department.
The wider UN system is a network of institutions with distinct mandates, budgets and governance arrangements. This distinction matters because statements about what the United Nations does may refer either to the core organisation established by the Charter or to the broader family of international organisations associated with it.
The UN Charter establishes principles governing the organisation's activities. These include the sovereign equality of member states, the peaceful settlement of disputes and restrictions on the threat or use of force except in circumstances recognised by the Charter, including self defence and Security Council action. The Charter also establishes commitments to international cooperation and human rights. The organisation is therefore not simply a world government.
It does not possess unlimited authority over sovereign states and normally depends upon member states for troops, funding, implementation and political support. Its effectiveness varies according to the willingness of states to cooperate and, particularly in security matters, the positions of the permanent members of the Security Council.
The General Assembly is the most broadly representative principal organ because each member state has a seat and a vote. It debates international questions and can adopt resolutions expressing the collective position of member states, although most General Assembly resolutions are not legally equivalent to binding domestic legislation. The Security Council has different powers under the Charter and can adopt decisions that member states are obligated to implement in relevant circumstances.
Its permanent members are China, France, Russia, the United Kingdom and the United States. The veto allows any permanent member to prevent adoption of a substantive Security Council resolution, making the Council both a central instrument of collective security and a reflection of the geopolitical realities of the postwar international system.
The United Nations has played roles in peacekeeping, humanitarian assistance, refugee protection, development, international law, public health and conflict prevention. UN peacekeeping operations are normally established through Security Council mandates and rely on personnel supplied by member states. Humanitarian agencies have responded to wars, famines, displacement and natural disasters. International agreements negotiated under UN auspices have addressed issues including human rights, refugees, environmental protection and arms control. The organisation therefore has functions extending well beyond preventing wars. Nevertheless, it does not control every international problem, and its effectiveness can be limited by disagreements between member states, insufficient resources, competing national interests and the veto structure of the Security Council.
The United Nations was created partly from lessons drawn from the failure of the League of Nations and the destruction caused by the Second World War. The founders sought an organisation with stronger participation by major powers and a more developed mechanism for collective security. Unlike the League, the United States became a founding member of the UN.
The organisation's creation also reflected the wartime cooperation of the major Allied powers, although that cooperation soon deteriorated as the Cold War developed. The United Nations consequently emerged simultaneously as an institution of postwar cooperation and as a forum in which the rival interests of the United States, Soviet Union and their respective allies could be expressed and contested.
The United Nations should therefore be understood as an international organisation rather than a supranational government with unrestricted authority. Its importance comes from providing an institutional forum in which states can negotiate, coordinate policies, establish international norms and respond collectively to crises. Its Charter supplies a legal and political framework, while its various organs and associated institutions perform specialised functions. The organisation's history has included both substantial achievements and serious limitations, particularly when powerful states disagree. Nevertheless, its creation in 1945 represented a major transformation in international organisation because it established a permanent global institution designed to provide mechanisms for cooperation after the unprecedented destruction of the Second World War.
