By the 1970s, the UN's budget for economic and social development programmes far outstripped its spending on peacekeeping. Since then, 80 former colonies have gained independence, including 11 trust territories that had been monitored by the Trusteeship Council.

UN membership grew significantly following widespread decolonization beginning in the 1960s. Its missions have consisted primarily of unarmed military observers and lightly armed troops with primarily monitoring, reporting and confidence-building roles. The organization's mission to preserve world peace was complicated in its early decades by the Cold War between the United States and Soviet Union and their respective allies. At its founding, the UN had 51 member states with the addition of South Sudan in 2011, membership is now 193, representing almost all of the world's sovereign states. Pursuant to the Charter, the organization's objectives include maintaining international peace and security, protecting human rights, delivering humanitarian aid, promoting sustainable development, and upholding international law. On 25 April 1945, 50 governments met in San Francisco for a conference and started drafting the UN Charter, which was adopted on 25 June 1945 and took effect on 24 October 1945, when the UN began operations. The UN was established after World War II with the aim of preventing future world wars, succeeding the League of Nations, which was characterized as ineffective. The UN is headquartered on international territory in New York City, and has other main offices in Geneva, Nairobi, Vienna, and The Hague (home to the International Court of Justice). It is the world's largest and most familiar international organization. The United Nations ( UN), particularly informally also referred to as the United Nations Organization ( UNO), is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmonizing the actions of nations.

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