The text below is from the charter of the United Nations:

WE THE PEOPLES OF THE UNITED NATIONS DETERMINED
to save succeeding generations from the [destruction] of war, which twice in our lifetime has brought untold sorrow to mankind, and
to reaffirm 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.

Source: http://www.un.org/en/documents/charter/preamble.shtml

What was the primary reason for the writing of this document?

to create an international organization based on collective security
to enforce the protection of human rights by member nations
to nullify previous international treaties and security agreements
to establish an international economic fund to support war refugees