What is the role of the United Nations in maintaining peace?

The League of Nations was created after World War I in an
attempt to give countries a way to solve problems without resorting to war, but was not
structured in a way that allowed this goal to be achieved. The United Nations was
founded after World War II as a second attempt to create an organization allowing
countries to gather and discuss differences and problems and work to find solutions
without resorting to fighting. It has the authority to intervene in situations with
mediators to try to resolve conflicts, with aid to support and assist persons being
affected or displaced by conflicts, and with troops if necessary to try to control and
end military actions. The United Nations also sponsors efforts to support economic
development, improvement of health care and other social programs, enforcement of
international law, and recognition of human rights.

The
Preamble, or introduction, to the Charter of the United Nations,
reads:

WE THE PEOPLES OF THE UNITED NATIONS DETERMINED

• to save succeeding generations from the scourge of war,
  which twice in our lifetime has brought untold sorrow to mankind,
  and


• to regain faith in fundamental human rights, in the
  dignity and worth of the human person, in the equal rights of men and women and of
  nations large and small, and


• to establish conditions
  under which justice and respect for the obligations arising from treaties and other
  sources of international law can be maintained, and


• to
  promote social progress and better standards of life in larger
  freedom,

AND FOR THESE ENDS

• to practice tolerance and live together in peace with one
  another as good neighbours, and


• to unite our strength to
  maintain international peace and security, and


• to ensure,
  by the acceptance of principles and the institution of methods, that armed force shall
  not be used, save in the common interest, and


• to employ
  international machinery for the promotion of the economic and social advancement of all
  peoples,

HAVE RESOLVED TO COMBINE OUR EFFORTS TO
ACCOMPLISH THESE AIMSAccordingly, our respective Governments, through representatives
assembled in the city of San Francisco, who have exhibited their full powers found to be
in good and due form, have agreed to the present Charter of the United Nations and do
hereby establish an international organization to be known as the United
Nations.