Answer:
I don't think the United Nations has been successful so far, in that aspect.
Step-by-step explanation:
Though the United Nations has made enormous efforts towards controlling and preventing conflicts and wars through peacekeeping and diplomacy, the situation in the last ten years shows its effort is still not enough.
Wars and conflicts in the middle East have gone on for years on end. The Syrian civil war has left many becoming refugees and their cities destroyed. The Israeli and Pakistani conflicts is still a concern and so are various other conflicts going on in the middle East.
The stockpiling of weapons of mass destruction by major superpowers and the development and testing of these weapons by countries like North Korea, is a pointer to a potential major war dubbed world war three by most people.