How did the Cold War change the role of the United Nations?

Before the Cold War, the United Nations was supposed to be
a body that would be able to maintain peace in the world.  It was supposed to represent
the consensus of all nations.  At the end of WWII, there were no formal rivalries
between any major countries and so it was hoped that the UN would represent all
countries in the world.

As the Cold War got started, this
fell apart.  The world started to split up into the Communist bloc and the US and its
allies.  This led to the UN being unable to do anything major because the two sides
would never agree.  So instead of being a major peacekeeping organization run on
consensus, the UN had to be content with doing minor, noncontroversial things like
UNICEF.