International armed forces were first used in 1948 to observe cease-fires in Kashmir and Palestine. Although not specifically mentioned in the UN Charter, the use of such forces as a buffer between warring parties pending troop withdrawals and negotiations—a practice known as peacekeeping—was formalized in 1956 during the Suez Crisis between Egypt, Israel, France, and the United Kingdom. Peacekeeping missions have taken many forms, though they have in common the fact that they are designed to be peaceful, that they involve military troops from several countries, and that the troops serve under the authority of the UN Security Council. In 1988 the UN Peacekeeping Forces were awarded the Nobel Prize for Peace.

During the Cold War, so-called first-generation, or “classic,” peacekeeping was used in conflicts in the Middle East and Africa and in conflicts stemming from decolonization in Asia. Between 1948 and 1988 the UN undertook 13 peacekeeping missions involving generally lightly armed troops from neutral countries other than the permanent members of the Security Council—most often Canada, Sweden, Norway, Finland, India, Ireland, and Italy. Troops in these missions, the so-called “Blue Helmets,” were allowed to use force only in self-defense. The missions were given and enjoyed the consent of the parties to the conflict and the support of the Security Council and the troop-contributing countries.

With the end of the Cold War, the challenges of peacekeeping became more complex. In order to respond to situations in which internal order had broken down and the civilian population was suffering, “second-generation” peacekeeping was developed to achieve multiple political and social objectives. Unlike first-generation peacekeeping, second-generation peacekeeping often involves civilian experts and relief specialists as well as soldiers. Another difference between second-generation and first-generation peacekeeping is that soldiers in some second-generation missions are authorized to employ force for reasons other than self-defense. Because the goals of second-generation peacekeeping can be variable and difficult to define, however, much controversy has accompanied the use of troops in such missions.

In the 1990s, second-generation peacekeeping missions were undertaken in Cambodia (1991–93), the former Yugoslavia (1992–95), Somalia (1992–95), and elsewhere and included troops from the permanent members of the Security Council as well as from the developed and developing world (e.g., Australia, Pakistan, Ghana, Nigeria, Fiji, India). In the former Yugoslav province of Bosnia and Herzegovina, the Security Council created “safe areas” to protect the predominantly Bosniak (Bosnian Muslim) population from Serbian attacks, and UN troops were authorized to defend the areas with force. In each of these cases, the UN reacted to threats to peace and security within states, sometimes taking sides in domestic disputes and thus jeopardizing its own neutrality. Between 1988 and 2000 more than 30 peacekeeping efforts were authorized, and at their peak in 1993 more than 80,000 peacekeeping troops representing 77 countries were deployed on missions throughout the world. In the first years of the 21st century, annual UN expenditures on peacekeeping operations exceeded $2 billion.

In addition to traditional peacekeeping and preventive diplomacy, in the post-Cold War era the functions of UN forces were expanded considerably to include peacemaking and peace building. (Former UN secretary-general Boutros Boutros-Ghali described these additional functions in his reports An Agenda for Peace [1992] and Supplement to an Agenda for Peace [1995].) For example, since 1990 UN forces have supervised elections in many parts of the world, including Nicaragua, Eritrea, and Cambodia; encouraged peace negotiations in El Salvador, Angola, and Western Sahara; and distributed food in Somalia. The presence of UN troops in Yugoslavia during the violent and protracted disintegration of that country renewed discussion about the role of UN troops in refugee resettlement. In 1992 the UN created the Department of Peacekeeping Operations (DPKO), which provides administrative and technical support for political and humanitarian missions and coordinates all mine-clearing activities conducted under UN auspices.

The UN’s peacekeeping, peacemaking, and peace-building activities have suffered from serious logistical and financial difficulties. As more missions are undertaken, the costs and controversies associated with them have multiplied dramatically. Although the UN reimburses countries for the use of equipment, these payments have been limited because of the failure of many member states to pay their UN dues.

Sanctions and military action

By subscribing to the Charter, all members undertake to place at the disposal of the Security Council armed forces and facilities for military sanctions against aggressors or disturbers of the peace. During the Cold War, however, no agreements to give this measure effect were concluded. Following the end of the Cold War, the possibility of creating permanent UN forces was revived.

During the Cold War the provisions of chapter 7 of the UN Charter were invoked only twice with the support of all five permanent Security Council members—against Southern Rhodesia in 1966 and against South Africa in 1977. After fighting broke out between North and South Korea in June 1950, the United States obtained a Security Council resolution authorizing the use of force to support its ally, South Korea, and turn back North Korean forces. Because the Soviet Union was at the time boycotting the Security Council over its refusal to seat the People’s Republic of China, there was no veto of the U.S. measure. As a result, a U.S.-led multinational force fought under the UN banner until a cease-fire was reached on July 27, 1953.

The Security Council again voted to use UN armed forces to repel an aggressor following the August 1990 invasion of Kuwait by Iraq. After condemning the aggression and imposing economic sanctions on Iraq, the council authorized member states to use “all necessary means” to restore “peace and security” to Kuwait. The resulting Persian Gulf War lasted six weeks, until Iraq agreed to comply with UN resolutions and withdraw from Kuwait. The UN continued to monitor Iraq’s compliance with its resolutions, which included the demand that Iraq eliminate its weapons of mass destruction. In accordance with this resolution, the Security Council established a UN Special Mission (UNSCOM) to inspect and verify Iraq’s implementation of the cease-fire terms. The United States, however, continued to bomb Iraqi weapons installations from time to time, citing Iraqi violations of “no-fly” zones in the northern and southern regions of the country, the targeting of U.S. military aircraft by Iraqi radar, and the obstruction of inspection efforts undertaken by UNSCOM.

The preponderant role of the United States in initiating and commanding UN actions in Korea in 1950 and the Persian Gulf in 1990–91 prompted debate over whether the requirements and spirit of collective security could ever be achieved apart from the interests of the most powerful countries and without U.S. control. The continued U.S. bombing of Iraq subsequent to the Gulf War created further controversy about whether the raids were justified under previous UN Security Council resolutions and, more generally, about whether the United States was entitled to undertake military actions in the name of collective security without the explicit approval and cooperation of the UN. Meanwhile some military personnel and members of the U.S. Congress opposed the practice of allowing U.S. troops to serve under UN command, arguing that it amounted to an infringement of national sovereignty. Still others in the United States and western Europe urged a closer integration of United States and allied command structures in UN military operations.

In order to assess the UN’s expanded role in ensuring international peace and security through dispute settlement, peacekeeping, peace building, and enforcement action, a comprehensive review of UN Peace Operations was undertaken. The resulting Brahimi Report (formally the Report of the Panel on United Nations Peace Operations), issued in 2000, outlined the need for strengthening the UN’s capacity to undertake a wide variety of missions. Among the many recommendations of the report was that the UN maintain brigade-size forces of 5,000 troops that would be ready to deploy in 30 to 90 days and that UN headquarters be staffed with trained military professionals able to use advanced information technologies and to plan operations with a UN team including political, development, and human rights experts.