Major Moments in UN History

The United Nations (UN) Charter enters into force following ratification by twenty-nine countries. The charter establishes the United Nations, a global intergovernmental institution dedicated to preventing future conflicts, fostering international cooperation, upholding universal human rights, promoting economic and social progress, and addressing humanitarian issues. It aims to replace the ineffectual League of Nations, created in 1920 and dissolved in 1946, after it failed to prevent the outbreak of World War II. The United Nations is composed of two primary bodies: the General Assembly (UNGA), the main policymaking and most representative UN body, and the Security Council (UNSC), the principal crisis-management body. Five countries—the United States, the Nationalist-led Republic of China (Taiwan), France, the Soviet Union, and the United Kingdom (UK)—hold permanent seats on the UNSC in 1945 and have veto power. (In 1971, the People’s Republic of China, mainland China, replaces the Republic of China at the United Nations and on the Security Council.)

UN members establish the Economic and Social Council to provide a central forum for discussing and addressing international economic and social issues, as well as cultural and health matters. These include poverty, inequality, education and, decades later, climate change and sustainable development. In 1946, the General Assembly also creates the UN International Children’s Emergency Fund (UNICEF)—later shortened to the UN Children’s Fund—to provide emergency aid to children and mothers in countries affected by World War II. In 1950, UNICEF’s mandate expands to address the long-term needs of children and women around the world, particularly in developing countries, and it becomes a permanent part of the UN system in 1953.

The World Health Organization (WHO) is established as the UN body responsible for guiding and coordinating international health policy. Its primary duties include developing partnerships with other global health initiatives, conducting research, setting norms, providing technical support, and monitoring health trends around the world. Over the following decades, the WHO solidifies its role as a global health leader, helping to eliminate malaria in more than a dozen countries where the disease was once endemic, as well as globally eradicate smallpox—the first human infectious disease to be completely eliminated. In the 1980s, the WHO launches a Global Program on AIDS after declaring it to be “a health disaster of pandemic proportions.”

The General Assembly passes the Uniting for Peace Resolution to bypass an expected Soviet veto on the Security Council that would have blocked UN efforts to defend South Korea against North Korea’s invasion. Months earlier, in July 1950, the Security Council had established the United Nations Command, placing international military forces under U.S. leadership to defend South Korea—the world’s first attempt at collective security under the UN system. The new resolution authorizes the General Assembly to recommend collective measures—including the use of force—and to convene emergency special sessions when the Security Council is paralyzed by a lack of consensus among its five permanent members. Although General Assembly recommendations are nonbinding, they can mobilize international action and carry significant political weight. The resolution is invoked thirteen times between 1951 and 2022, including during the 1956 Suez Crisis and Russia’s 2022 invasion of Ukraine.

To address the plight of people fleeing primarily political and religious persecution in Europe, nineteen countries—excluding the United States—sign the Convention Relating to the Status of Refugees, also known as the 1951 Refugee Convention. The signing takes place during the UN Conference of Plenipotentiaries on the Status of Refugees and Stateless Persons in Geneva. Rooted in Article 14 of the UDHR, which states that, “Everyone has the right to seek and to enjoy in other countries asylum from persecution,” the convention defines the term “refugee” and outlines refugees’ rights and the legal obligations that states have to protect them. The UN High Commissioner for Refugees is responsible for overseeing implementation of the convention. It officially enters into force on April 22, 1954, and remains the cornerstone of modern international refugee law. The United States does not ratify the convention, but it does join its 1967 Protocol, which incorporates much of the convention’s text, protects refugees, and prohibits returning refugees to danger.

After Egypt nationalizes the Suez Canal Company—leading to military intervention by Israel, France, and the UK—the United Nations deploys an armed peacekeeping force to act as a buffer between Egyptian and Israeli forces and secure a ceasefire. While the UN Emergency Force (UNEF) is armed with light defensive weapons, it is restricted from using force other than in self-defense. UNEF remains in Egypt until May 1967, when it is forced to withdraw at the request of the Egyptian government. A second UNEF mission is established in 1973 in response to the Yom Kippur War between Israel and a coalition of Arab states led by Egypt and Syria and remains in Egypt for six years.

The International Atomic Energy Agency (IAEA) is founded in response to concerns about nuclear weapons and the escalating U.S.-Soviet arms race. The agency’s creation comes four years after U.S. President Dwight D. Eisenhower’s “Atoms for Peace” speech to the General Assembly, in which he proposed the creation of an international body to promote the peaceful use of atomic power. Unanimously approved by more than eighty countries, the IAEA’s charter outlines a three-part mission: nuclear verification and security, safety, and technology transfer. While the agency is an independent intergovernmental organization, it maintains relationships with both the General Assembly and the Security Council, to which it reports. Over the coming decades, the IAEA plays a critical role in coordinating the global response to both the Chernobyl and Fukushima nuclear disasters, as well as monitoring Iran’s contentious nuclear program via inspections and safeguards.

Shortly after gaining independence from Belgium, the Democratic Republic of Congo (DRC) appeals to the United Nations to help protect its political and territorial sovereignty. The Security Council responds by authorizing the UN Operation in the Congo (ONUC), a peacekeeping operation intended to provide military and technical assistance until Congolese forces are capable of defending their own territory. By 1960, the Congo faces a secession crisis as the province of Katanga seeks independence. The conflict unfolds amid Cold War tensions, with the United States and the Soviet Union at odds over its resolution. In 1961, UN Secretary-General Dag Hammarskjöld dies under mysterious circumstances in a plane crash en route to negotiate peace in the region. Shortly after, the Security Council passes Resolution 169, siding with the Congolese government. In 1962, the ONUC launches operations to prevent Katanga’s secession. Katanga surrenders in January 1963 and the ONUC withdraws from the DRC in June 1964.

U.S. intelligence discovers that Cuba has allowed the Soviet Union to build nuclear missile installations on the island, prompting U.S. President John F. Kennedy to demand their removal and impose a naval quarantine of Cuba. His actions trigger a thirteen-day standoff. With fears of a nuclear war looming, the United States and the Soviet Union negotiate via back channels. As the crisis continues, Kennedy secretly agrees to withdraw U.S. nuclear missiles from Turkey within months and pledges not to invade Cuba if the Soviet Union withdraws its missiles. Soviet Premier Nikita Khrushchev accepts the deal and announces that he will order the missiles removed. Throughout the crisis, the United Nations—led by Secretary-General U Thant—serves as a mediator, privately facilitating communication between both sides. While largely on the margins, the United Nations’ involvement provides a diplomatic channel that helps defuse one of the most dangerous confrontations of the Cold War.

The United Nations adopts the International Covenant on Civil and Political Rights (ICCPR) and the International Covenant on Economic, Social and Cultural Rights (ICESCR) to further codify human rights. Originally drafted as one document, these covenants are ratified separately to address ideological differences primarily between UN member states during the Cold War. These two treaties legally bind states to uphold human rights, including the right to work, education, life, and religion. The ICESCR enters into force in January 1976, and the ICCPR in March of that same year. Along with the UDHR, the ICCPR and ICESCR form the core foundation of international human rights law.

As the Palestine Liberation Organization (PLO) grows in influence, the General Assembly adopts Resolution 3210 (XXIX), recognizing the PLO as the sole legitimate representative of the Palestinian people. Days later, the assembly grants the PLO observer status, allowing them to participate in the work of the General Assembly and other UN bodies. In 1975, the assembly establishes the Committee on the Exercise of the Inalienable Rights of the Palestinian People to promote Palestinians’ right to self-determination, sovereignty, and national independence. The decision to recognize the PLO elevates the group’s international political standing and legitimacy. In 1988, the designation of “Palestine” officially replaces the PLO within the UN system. Despite these moves, the issue of Palestinian statehood remains a subject of heated debate.

After receiving initial ratification from 197 countries, the Montreal Protocol takes effect—the first and only UN treaty to achieve universal ratification. It is also the first international treaty to address a planetary-scale environmental issue. The protocol requires states to stop producing substances that damage the Earth’s ozone layer, such as chlorofluorocarbons (CFCs), which are used in refrigerants, aerosols, and other applications. The protocol helps to eliminate nearly 99 percent of CFCs and is considered one of the most effective international climate agreements. In 2016, all states party to the protocol agree via the Kigali Amendment to also reduce their production of hydrofluorocarbons, powerful greenhouse gases that contribute to climate change.

Following Iraq’s invasion of Kuwait, the Security Council condemns the move and issues a resolution demanding Iraq’s immediate and unconditional withdrawal to pre-invasion positions. When Iraq fails to comply, the Security Council imposes a comprehensive trade embargo on Baghdad, which excludes humanitarian aid. As tensions escalate, the Council authorizes member states in November to use “all necessary means” to enforce withdrawal by January 15, 1991. After Iraqi leader Saddam Hussein refuses, a UN-backed, U.S.-led coalition attacks Iraq, and the United States declares a ceasefire the following month. In April 1991, the Council deploys the UN Iraq-Kuwait Observation Mission (UNIKOM) to monitor the demilitarized zone between Iraq and Kuwait until 2003. In 1995, the United Nations establishes the Oil-for-Food Program to allow Iraq to sell oil in exchange for humanitarian goods, while preventing the development of weapons of mass destruction. However, the program is plagued by widespread violations and corruption, including by Security Council members.

In Rio de Janeiro, Brazil, the UN Conference on Environment and Development—known as the Earth Summit—brings together political leaders, scientists, and media and NGO representatives from 179 countries to address the effects of human activities on the environment. The summit produces several major agreements, including the Rio Declaration on Environment and Development and Agenda 21, a blueprint for achieving sustainable development. It also establishes two major treaties: the Convention on Biological Diversity and the UN Framework Convention on Climate Change (UNFCCC). The UNFCC, signed by 154 countries, including the United States, is the first global treaty to explicitly address climate change, with signatories pledging to combat “dangerous human interference with the climate system.” It establishes the Conference of the Parties, an annual global forum that leads to subsequent binding climate agreements like the Kyoto Protocol and the Paris Agreement.

The Security Council sets up the International Criminal Tribunal for the former Yugoslavia (ICTY) to prosecute those responsible for war crimes and other “serious violations of international humanitarian law” during the Balkan wars of the 1990s. The ICTY can determine culpability in four main areas: major violations of the 1949 Geneva Conventions, breaches of the laws or customs of war, crimes against humanity, and genocide. It is the first ad hoc international war crimes tribunal since the Nuremberg and Tokyo trials in the wake of World War II. In 2007, the United Nations’ own top court, the International Court of Justice, delivers a landmark ruling confirming that the 1995 massacre of more than eight thousand Bosnian Muslim men and boys in Srebrenica by Bosnian Serb forces was an act of genocide. The ICTY indicts a total of 161 people, including the leading perpetrators of the genocide during the Bosnian War, before its mandate ends in 2017.

The United Nations establishes the International Criminal Tribunal for Rwanda (ICTR) months after approximately eight hundred thousand Rwandans—primarily members of the Tutsi minority—are killed during a period of about one hundred days. The genocide unfolds after most UN peacekeeping forces withdraw from the country. The ICTR’s purpose is to prosecute individuals responsible for the killings and other serious violations of international humanitarian law. Between 1995 and 2015, when its mandate ends, the tribunal indicts ninety-three individuals, including high-ranking military and government officials. The ICTR is the first institution to define rape in international criminal law and recognize it as a means of perpetrating genocide. It is also the first international tribunal to hold members of the media accountable for their involvement in international crimes. In 2010, the Security Council establishes the International Residual Mechanism for Criminal Tribunals to carry on the residual functions of both the ICTY and the ICTR.

The Security Council authorizes an international civil presence in the breakaway Serbian province of Kosovo, known as the UN Interim Administration Mission in Kosovo (UNMIK). The decision follows the end of the NATO bombing campaign against Serbia—a part of the Federal Republic of Yugoslavia—and the cessation of the Serbian government’s large-scale violence targeting ethnic Albanians in Kosovo. UNMIK’s mandate is to “ensure conditions for a peaceful and normal life for all inhabitants of Kosovo and advancement of regional stability in the Western Balkans.” Working closely with NATO, its responsibilities include promoting security and stability, safeguarding human rights, and establishing provisional institutions of self-government in Kosovo, home to a majority ethnic Albanian population and small enclaves of ethnic Serbs. While the mission succeeds at stabilizing Kosovo after the war and restoring law and order, some critics say it falls short of building a fully functional and inclusive political system.

At the UN Millennium Summit in New York, one of the largest-ever gatherings of world leaders at the time, 189 countries adopt the Millennium Declaration. It commits countries to combating issues including hunger, disease, poverty, and environmental degradation. The declaration forms the basis for the eight Millennium Development Goals (MDGs), which focus on directing wealthy countries’ resources toward eradicating poverty and improving global health in poor countries. Each goal has targets set for 2015 and indicators to monitor progress. By 2015, when the MDGs expire, experts agree they were largely successful, particularly in reducing extreme poverty and combating diseases, though progress varied across goals and regions.

At the International Conference on Financing for Development in Monterrey, Mexico, the General Assembly adopts the Monterrey Consensus [PDF]. It emphasizes the shared responsibility of developing countries to pursue economic and social development and of wealthy nations to support them through open trade and increased financial aid. The agreement focuses on six areas for financing development: mobilizing domestic financial resources in developing countries, setting a target of 0.7 percent of gross national incomes for donor countries’ official development assistance, increasing international financial and technical cooperation, encouraging international trade, providing external debt relief, and addressing systematic issues. The United States, under President George W. Bush, strongly backs the effort, which lays the groundwork for the Millennium Challenge Corporation—an independent U.S. foreign aid agency that partners with developing countries that have demonstrated good governance and sound economic policies.

A truck bomb kills twenty-two people, including the top UN envoy to Iraq, Sérgio Vieira de Mello, and badly damages the Canal Hotel in Baghdad, Iraq—a base for some three hundred UN personnel. Abu Musab al-Zarqawi, leader of the terrorist organization Jama’at al-Tawhid wal-Jihad, claims responsibility for what is the first major terrorist attack to target the United Nations. The incident highlights the United Nations’ precarious position after accepting a lead role in Iraq’s democracy and nation-building efforts following the 2003 U.S.-led invasion—a war that many UN members opposed. A week after the attack, the Security Council unanimously passes a resolution [PDF] declaring that “attacks knowingly and intentionally directed against” humanitarian or peacekeeping personnel “constitute war crimes.”

At a time of multiple conflicts, the General Assembly endorses the Responsibility to Protect (R2P) doctrine at the UN World Summit. R2P asserts that sovereign countries have a fundamental responsibility to protect their citizens and if they fail to do so, the Security Council can use its existing UN Charter authority to intervene—including by using military force—to protect innocent civilians and prevent large-scale loss of life. The doctrine establishes a heightened political priority for humanitarian intervention, provided the Security Council authorizes it in particular situations. However, some critics argue that R2P risks undermining state sovereignty and encourages foreign interference by the Security Council in states’ internal affairs. Most notably, the doctrine is used to justify NATO-led intervention in Libya’s civil war in 2011, after the Security Council authorizes the use of force to protect civilians from Muammar al-Qaddafi’s crackdown—a decision that proves controversial among UN member states. More than a decade later, Libya remains riven by civil war.

The General Assembly votes overwhelmingly to adopt a resolution establishing the Human Rights Council (UNHRC), which is responsible for “strengthening the promotion and protection of human rights around the globe,” as well as addressing human rights violations. The UNHRC replaces the Commission on Human Rights, created in 1946, which faced widespread criticism for letting countries with poor human rights records become members. The UNHRC meets at least three times a year and reviews the records of all UN members in a process known as Universal Periodic Review. In 2009, under President Barack Obama, the United States secures a seat on the council and is reelected in 2012. The council faces a bout of criticism in 2013 after Algeria, China, Russia, Saudi Arabia, and Vietnam are elected members by the General Assembly, despite checkered rights records. In 2018, President Donald Trump withdraws the United States from the UNHRC, citing bias against Israel—particularly a standing agenda item on the human rights situation in the Palestinian territories. The United States gains an elected seat on the UNHRC in 2021, but Trump withdraws the country again after he returns to office in 2025.

A catastrophic 7.0-magnitude earthquake strikes Haiti, killing an estimated 220,000 people and displacing 1.5 million more. The quake deals a severe blow to the country’s already shaky economy and infrastructure, collapsing the headquarters of the UN Stabilization Mission in Haiti (MINUSTAH) that was launched in 2004 to restore political order. In response, the Security Council endorses Secretary-General Ban Ki-moon’s recommendation to increase the UN peacekeeping presence in Haiti to support the country’s stability, recovery, and reconstruction efforts. UN and partner organizations launch a $575 million flash appeal for emergency humanitarian assistance, while the Security Council authorizes an increase of 3,500 troops and police to reinforce MINUSTAH’s efforts. The quake is the deadliest disaster in UN peacekeeping history, resulting in the deaths of 102 UN personnel, including head of MINUSTAH Hédi Annabi and 96 peacekeepers. In the quake’s aftermath, Haiti suffers a major cholera outbreak—later traced to UN peacekeepers—leading to significant criticism of the United Nations’ handling of the crisis.

Nearly a week after Iran, the five permanent members of the Security Council, and European Union (EU) representatives reach the Joint Comprehensive Plan of Action (JCPOA), the Council formally endorses the agreement via Resolution 2231. The JCPOA, also known as the Iran nuclear deal, is negotiated in response to growing concerns about nuclear proliferation in the Middle East. It aims to ensure that Iran’s nuclear program is kept peaceful by offering sanctions relief in exchange for restrictions on Tehran’s nuclear activities, including uranium enrichment limits monitored by the IAEA. Nuclear talks with Iran remain in a state of flux over the next several years as efforts to revive the JCPOA continue following the 2018 U.S. withdrawal and subsequent violations by Iran.

The General Assembly adopts the Global Compact for Safe, Orderly and Regular Migration, the first-ever global agreement on a common approach to international migration. The nonbinding agreement [PDF] outlines twenty-three objectives to support international cooperation, including reducing migrant smuggling, ensuring migrants’ access to basic services, and using detention only as a last resort. While proponents laud the agreement as a step forward in global migration governance, critics view it as a challenge to state sovereignty. Some countries that initially sign or support the agreement later withdraw from the process or decline to implement it, including Australia, Austria, Hungary, and Poland. Despite efforts by states, by the end of 2024, there are an estimated 123.2 million forcibly displaced people worldwide.

The WHO director-general announces that COVID-19—first detected in December 2019 in Wuhan, China—constitutes a pandemic. The United Nations launches a coordinated response that includes health, humanitarian, and socioeconomic planning via various UN bodies. UN agencies also help lead the global COVAX initiative to ensure equitable access to COVID-19 vaccines around the world. Meanwhile, UN Secretary-General António Guterres calls for a global ceasefire so countries can focus on their public health response. The United Nations issues both a Global Humanitarian Response Plan and a socioeconomic recovery framework to mitigate the pandemic’s effect on the world’s most vulnerable countries. Despite these global efforts, however, the disease kills more than seven million people over the next few years, per the WHO.

During its eleventh emergency special session, the General Assembly overwhelmingly adopts a nonbinding resolution condemning Russia’s February 2022 invasion of Ukraine. The session is triggered by the rarely used Uniting for Peace resolution after the Security Council fails to pass a similar resolution due to a Russian veto. In a vote of 141–5, with 35 abstentions, the assembly “deplores in the strongest terms” Russia’s unprovoked aggression, demands that Russia immediately cease fighting and unconditionally withdraw its forces from Ukraine, and calls on Moscow to reverse its recognition of Ukraine’s Donetsk and Luhansk regions as independent. On April 7, the assembly suspends Russia’s membership rights in the UNHRC following reports of gross and systematic human rights violations.

On October 7, Hamas launches a surprise assault on southern Israel, killing nearly 1,200 people and taking about 250 hostages. In response, Israel declares war with the stated goal of eradicating the group, marking the start of intense military operations. As the conflict continues unabated, the humanitarian situation in Gaza grows more dire. UN agencies—particularly the World Food Program, the Office for the Coordination of Humanitarian Affairs, and the UN agency for Palestinian refugees—coordinate the provision of humanitarian aid and make repeated calls for ceasefires and humanitarian pauses. However, UN funding shortfalls and restricted access to Gaza hamper aid efforts, which are further hindered by ongoing crises in Ukraine and Sudan. By the end of 2024, the United Nations reports that 181 aid workers have been killed in Gaza, now considered the deadliest location for humanitarian personnel in the world. Reflecting the scale of the crisis, the UN-backed global hunger monitor declares in August 2025 that an “entirely man-made” famine is occurring in and around Gaza City, previously the enclave’s largest population center.