When you walk into a Model UN chamber, you are sitting inside an idea that is exactly eighty-one years old this year — and that nearly didn't survive its first decade. Knowing how the institution you are simulating was built changes how you simulate it.

Learning objectives
By the end of this module, you will be able to:
In this guide
  1. Before 1945 — the failed precedent
  2. San Francisco, 1945
  3. The Charter and what it changed
  4. The six principal organs
  5. Eight milestones that shaped the UN
  6. The UN today — and its critics
  7. Why simulating it still matters

Before 1945 — the failed precedent

The League of Nations, established by the Treaty of Versailles in 1919, was the first attempt to build a permanent body for collective security. It had a Council, an Assembly, a Secretariat, and a court. It also had three structural problems that, in retrospect, made its collapse predictable.

First, the United States, despite being its principal architect under Woodrow Wilson, never joined — Congress refused to ratify the Treaty. Second, the League had no enforcement mechanism beyond moral pressure, and moral pressure proved insufficient against Japanese aggression in Manchuria, Italian aggression in Ethiopia, and German aggression in the Rhineland. Third, the Council operated on unanimity, meaning a single member could block any action.

By 1939, the League was effectively defunct. Its failure was the design constraint the United Nations was built to solve.

San Francisco, 1945

The blueprint was drafted at Dumbarton Oaks (1944) and finalised at Yalta (February 1945), where the Big Three — Roosevelt, Churchill and Stalin — agreed on the structure of what would become the Security Council. Between 25 April and 26 June 1945, fifty nations met at the San Francisco War Memorial Opera House and signed the Charter. The UN officially came into existence on 24 October 1945, when the Charter was ratified — a date now observed annually as United Nations Day.

Three structural choices distinguished the UN from the League:

The Charter and what it changed

The UN Charter is structured into 19 chapters and 111 articles. The opening words — "We the peoples of the United Nations…" — deliberately echo the US Constitution; the choice signalled that this was a project of peoples as well as states. Article 1 sets out the four purposes of the UN: maintaining peace, developing friendly relations, achieving cooperation on global problems, and serving as a centre for harmonising the actions of nations.

The Charter changed the international system in three ways. First, it made aggression illegal under Article 2(4), which forbids the use of force against the territorial integrity of any state. Second, it created universal collective security through Chapter VII. Third, it institutionalised diplomacy as a permanent practice — for the first time, every member state had a continuous diplomatic relationship with every other member state, mediated through a single shared institution.

The six principal organs

The UN today operates through six principal organs established by the Charter. Most MUN simulations focus on the first two; the others are no less important.

1. The General Assembly

193 member states, one vote each. Universal membership; the most representative body in international life. Adopts non-binding resolutions on the full range of international issues. The Assembly has 6 main committees plus the plenary; YIMUN 2026 simulates the plenary.

2. The Security Council

15 members — 5 permanent (P5) with veto, 10 non-permanent elected for two-year terms. The only UN body whose resolutions are legally binding under Chapter VII. The deadlock-prone but consequential heart of the system.

3. The Economic and Social Council (ECOSOC)

54 members. Coordinates the economic, social and environmental work of the UN system. Hosts the High-Level Political Forum on Sustainable Development.

4. The International Court of Justice

15 judges, seated at The Hague. The principal judicial organ — settles legal disputes between states and gives advisory opinions to the General Assembly.

5. The Secretariat

The international civil service that runs the UN. Headed by the Secretary-General, who serves a five-year renewable term. Currently António Guterres of Portugal (since 2017).

6. The Trusteeship Council

Effectively dormant since 1994 — the original trust territories have all become independent. Retained on paper, with the power to be reactivated.

Eight milestones that shaped the UN

1948 — The Universal Declaration of Human Rights

Drafted under Eleanor Roosevelt's chairship. Not legally binding in itself, but the foundation of all subsequent international human rights law. Article 1: "All human beings are born free and equal in dignity and rights."

1950 — The Korean War

The first and almost only deployment of UN forces under unified command, made possible because the Soviet Union was boycotting the Security Council and could not veto.

1956 — The Suez Crisis and the first peacekeeping mission

UN Emergency Force (UNEF) — the first armed peacekeeping mission. The model that has produced over 70 missions since.

1960 — Decolonisation Resolution 1514

The General Assembly's Declaration on the Granting of Independence to Colonial Countries. Catalysed the wave of decolonisation that nearly tripled UN membership over the next two decades.

1972 — The Stockholm Conference on the Human Environment

The first major UN environmental conference; founded UNEP and started the trajectory that led, fifty years later, to the Paris Agreement.

1989–1991 — End of the Cold War

The Security Council, paralysed by superpower veto for forty years, briefly became functional. The UN-authorised Gulf War coalition in 1991 was the first real test of post-Cold War collective security.

2000 — The Millennium Development Goals

Eight time-bound goals on poverty, education, health and the environment. Largely achieved or partially achieved by 2015. The first time the UN system organised global development around measurable targets.

2015 — The Paris Agreement and the Sustainable Development Goals

The COP21 climate agreement and the SDGs adopted at the same General Assembly. The most ambitious package of UN-led commitments since 1945, defining the trajectory of multilateral cooperation through to 2030.

The UN today — and its critics

The UN today has 193 member states, an annual regular budget of roughly $3.5 billion (with peacekeeping budgeted separately at around $6 billion), more than 35,000 staff worldwide, and a footprint that includes specialised agencies — WHO, UNESCO, UNICEF, UNHCR, UNDP, FAO, ILO — operating in nearly every country on Earth.

It is also under sustained criticism. The veto continues to paralyse the Security Council on Syria, Ukraine, Gaza and almost every conflict that touches the interests of a P5 power. The composition of the Security Council reflects the geopolitics of 1945 rather than 2026 — Africa has no permanent seat, India and Brazil have none, Germany and Japan have none. Reform has been on the table since the 1990s and shows no sign of resolution.

And yet the UN persists, in part because the alternative — an international system without a permanent forum — is worse. Almost every framework that has shaped the modern world, from human rights to climate cooperation to peacekeeping, traces back through it.

Why simulating it still matters

It would be easy to argue that an institution this contested is not worth simulating. The argument would be wrong. The case for MUN, refined down to its essentials, has three parts.

First, the format teaches the cluster of skills that the institution itself was built around — structured negotiation, calibrated language, multilateral compromise. Whatever you think of the UN's record, those skills have outlasted every political fashion since 1945, and they will outlast the next.

Second, simulation builds empathy in a way reading does not. After three days of arguing for a country whose interests are not your own, you understand multilateralism from the inside. That perspective is vanishingly rare among adults; it is one of the few things a teenager can acquire that is genuinely difficult to acquire later.

Third — and this is the part the brochures don't say — MUN matters because diplomacy itself matters. The skill of disagreeing with someone across the table without breaking the relationship is the skill on which every international agreement, every peace negotiation, every climate accord ultimately rests. It is also the skill on which most of adult life rests. The UN happens to be where the world practises it at the highest level. Walking into the chamber and trying yourself against that standard is one of the most valuable things a young person can do.

One thing to remember

You do not have to believe the UN is perfect to take it seriously. Most professional diplomats don't either. The point is that it is the room — and the rules of that room are still the rules of the world.

Self-assessment · Module 13

Practice what you've learned.

This is a context module — it is meant to inform every other module you have already done. The exercises are short and reflective rather than mechanical.

  1. The League/UN diff. In one paragraph, explain the three structural differences between the League of Nations and the United Nations.
  2. Six organs from memory. List the six principal organs of the UN in the order established. For each, state in one sentence what it does today.
  3. Milestone choice. Of the eight milestones in this module, pick the one you find most consequential. Write a 200-word case.
  4. The critic's response. Write a one-paragraph response to the claim that the UN is broken — using only what is in this module. Be honest about the weaknesses.
  5. Why simulate. In one sentence, explain to a sceptical friend why MUN — and the UN itself — is still worth taking seriously.
How to grade yourself: If a friend with no MUN experience reads exercises 4 and 5 and finds them persuasive, the module has worked.