How was the united nations designed to prevent global wars?

Answer 1

In the post-World War II era, the United Nations was formed intentionally to prevent any further global wars (and even smaller conflicts). To achieve this end, the designers of the "U.N." sought to engage the world's nations in a formal, public, ongoing discussion of world problems and regional tensions, to develop a process by which grievances would be brought into a global-public forum for the sake of peaceful resolution, and to introduce democratic principles into the world-community that would enable all nations to work as a unified whole rather than as isolated competitors.

Answer 2

Historically... the United Nations has never prevented any war, that any two or more nations so threatening, or so involved, didn't want to avoid or stop on their own.