United Nations: Mission and Structure: U.N. established in 1945 as a peacekeeping organization. Description of 5 main components of the United Nations: U.N. General Assembly, U.N. Security Council, U.N. International Court of Justice, U.N. Economic and Social Council, and the U.N. Secretariat. The Security General of the U.N. defined as the leader/spokeperson of the U.N. who organizes meetings, writes reports, and reports the decisions/opinions of the U.N. The League of Nations identified as an earlier peacekeeping organization formed in 1920 which the U.S. did not join and was dissolved due to numerous flaws.