The Charter of the United Nations was agreed to during the war at the United Nations Conference on International Organization , held between April and July 1945 . The Charter was signed by 50 nations on 26 June ( Poland had its place reserved and later became the 51st " original " signatory ) , and was formally ratified shortly after the war on 24 October 1945 . In 1944 , the United Nations was formulated and negotiated among the delegations from the Soviet Union , the United Kingdom , the United States and China at the Dumbarton Oaks Conference where the formation and the permanent seats ( for the " Big Five " , China , France , the UK , US , and USSR ) of the United Nations Security Council were decided . The Security Council met for the first time in the immediate aftermath of war on 17 January 1946
United Nations Conference on International Organization
United Nations Conference on International Organization
Allies of World War II