United Nations Peacekeeping Forces, agents of the United Nations (UN) who help to maintain or restore peace in regions of conflict. The peacekeeping forces comprise either unarmed observers or lightly armed military personnel from UN member nations. They traditionally enter conflicts after the combatants have declared a truce but before they have signed a formal peace treaty. The United Nations peacekeeping forces won the Nobel Prize for peace in 1988.

The first major UN peacekeeping mission took place in the Middle East in 1948. That year Britain withdrew from Palestine—which it had controlled since 1922—and the UN divided the country into two separate nations, Palestine and Israel. The five Arab countries surrounding Israel—Lebanon, Syria, Iraq, Transjordan (now Jordan), and Egypt—almost immediately attacked the new nation. After several weeks of war between Israel and its neighbors, the UN helped to negotiate a truce. However, tensions continued to run high, so the organization sent in a team of unarmed observers to help maintain the truce. The action proved effective, and since then the UN has often sent observers to regions of recent conflict.

In 1956 the United Nations armed its peacekeeping forces for the first time. The forces successfully helped to settle the Suez Crisis, an armed conflict between Egypt and the combined forces of France, Britain, and Israel over control of the Suez Canal. The UN secretary general at the time, Dag Hammarskjöld, established guidelines for the peacekeeping forces that remain intact today. Under these principles, UN forces may only initiate peacekeeping activities if all parties in the conflict agree to their presence. In addition, the troops may not use violence to accomplish their mission, only negotiation; the troops must serve under the exclusive command of the UN Security Council; all member nations of the UN must financially support the forces; and armed troops may fire their weapons only in self-defense. Individual soldiers serving on peacekeeping missions wear the uniform of their own country. They also wear a distinctive blue hat or helmet to identify them as part of the peacekeeping forces.

During the 1980s and 1990s UN forces helped to restore peace in several regional conflicts. Their accomplishments included helping to maintain cease-fires following the Iran-Iraq War in 1988 and following the wars in Croatia and Bosnia and Herzegovina during the mid- and late-1990s (see Wars of Yugoslav Succession). Since 2000, UN peacekeepers have worked to restore stability in East Timor, Darfur (a region of Sudan), Liberia, Côte d'Ivoire, Haiti, and Burundi. See also International Relations.