While the first answer is a good one, it does not cover one of the major ways that, according to scholars of International Relations (IR), the UN works to keep peace in the world. Some IR scholars aregue that the sort of peacekeeping efforts outlined above are not the important ones. These scholars say that such organizations can never do much to ensure peace through peacekeeping.
Instead, they say, the UN helps to keep the peace through such things as UNICEF and the World Health Organization. These types of organizations help keep peace in the following ways:
- They help to reduce the conditions that might lead to war. In other words, by improving the material lives of people in various countries, these organizations hope to make the countries more prosperous, more stable, and less likely to go to war.
- They help to build ties between various countries. IR scholars of this school of thought emphasize that the UN helps keep peace simply by tying the various countries together at a variety of levels. The more chances that (for example) the US and China have to work together on issues like health, the more connections are built between the two countries and the less likely they are to go to war.
These IR scholars, then, hold that the UN keeps the peace more through these roundabout ways than through peacekeepers and collective security.
The United Nations has sponsored dozens of peacekeeping missions since its founding in the wake of World War II. Troops under the UN banner have been sent to war-torn areas from Palestine to Rwanda. They have had varying success, and in several notable cases, including Rwanda, Bosnia-Herzegovina and Somalia, were largely powerless to halt widespread bloodshed. In other cases, including the Belgian Congo in the 1960s, UN troops were able to maintain peace, at least temporarily. The United Nations, particularly the Security Council, has also served as a forum for airing grievances during the Cold War, and the body has been instrumental in negotiating peace settlements in several conflicts. The United Nations has also participated in arms limitation and nuclear non-proliferation efforts. Overall, the success of the United Nations as a peacekeeping body has been mixed. While no large-scale global conflict, the kind of war the UN was chartered to prevent, has broken out since 1945, it is difficult to know precisely how instrumental the UN has been. Additionally, UN peacekeepers and envoys have struggled to maintain peace in regions where the situation had deteriorated past the point of control.