Upvote:-1
The United Nations has helped in various situations, but there aren't many where they have been the major presence in solving conflict. However, they have done good, such as by using pressure to encourage North/South Sudan talks.
Upvote:3
What comes to my mind is the Suez Crisis of 1956. After a series of engagements between Israeli and Egyptian forces, mostly on the Sinai Peninsula, a UN force called the United Nations Emergency Force was sent in to stop further hostilities.
This was during the cold war, when Israel was backed by the US, of course, while Egypt had the support of the Soviet Union. Relations between those two superpowers were not too good then. Therefore, I would say that there were parties on the brink of war (while others, Israel and Egypt, already actuall were at war) and count this an example of the UN "defusing", as you put it, a highly tense situation.