It is pity I did not see more of such sections (p.255-258) in this volume.
The United Nations (UN) went through the following (not necessarily in chronological order):
1. wrangling elections for the first Secretary General (a Norwegian candidate favoured by the then Soviet Union)
2. Iran crisis
3. Berlin Blockade
4. Korean War
For 2-3, the UN could do nothing since those involved were the superpowers themselves. (This was to be repeated in the 1962 Cuban Missile Crisis.) The reason why the US could get the UN nod to enter the Korean peninsula was because the USSR was absent from the Security Council at that pivotal period. (Nevertheless, the book still paints the conflict as a US failure.) The Cold War had paralysed the UN.
6. Arab-Israeli war (first)
The UN stepped in after the conflict began to help soothe and cease the hostilities. Note that this is a distinct, and very much poorer than preventing the onset of any war. In the other parts of the book, the UN was described as a tool for the US in creating contemporary Israel. The Jewish lobby was singled out for influencing President Truman’s efforts. (The role of the Jewish lobby can be further explored. This is in part because of the American lobbying culture. On another note, it potentially answers an earlier question on how much political opinion/pressure was on Truman in effecting efforts leading to the Cold War in Europe.)