Pope Pius XII, Christmas Eve address to the Roman Curia, Dec. 24, 1945:
"With an abundance of experience, good will, political wisdom and organizational power, at a level never seen before, preparations have begun for an organization dedicated to world peace. Never before have public leaders found themselves before an undertaking so vast and complex because of the number, importance and difficulty of the questions to be resolved nor so serious for the breadth and depth of its effects for the good or bad, such as giving back to humanity -- after three decades of world wars, economic catastrophes and excessive impoverishment -- order, peace and prosperity. Noble and formidable is the responsibility of those who are preparing to carry forward such a gigantic work."
--->Pius XII and UN: "Immediately after his election, Pius XII issued a call for a peace conference of European leaders. His peace plan was based on five points: the defense of small nations, the right to life, disarmament, some new kind of League of Nations, and a plea for the moral principles of justice and love."---National Catholic Register
Note / Caveat: This question of a United Nations as one means to assist nations to communicate with one another with a view to preventing another world war and other atrocities must, for a Catholic, not be confused with any so-called "New World Order" which might seek to impose a pseudo-peace on the world based on secularist Enlightenment presuppositions and trans-value all traditional values in that direction. Pope Benedict the XV (15th) warned:
“The advent of a Universal Republic, which is longed for by all the worst elements of disorder, and confidently expected by them, is an idea which is ripe for execution. From this Republic, based on the principles of absolute equality of men and community of possessions, would be banished all national distinctions, nor in it would the authority of a father over his children, or of the public power over the citizens, or of God over human society, be any longer acknowledged. If these ideas are put into practice there will inevitably follow a reign of unheard-of terror.” -Moto Proprio, Bonem Sane, July 25, 1920 (emphasis mine)