Background (pre-1941) 

• In the century prior to the UN's creation, several international organizations such as the International Committee of the Red Cross were formed to ensure protection and assistance for victims of armed conflict and strife.

• During World War I, several major leaders, especially U.S. President Woodrow Wilson, advocated for a world body to guarantee peace. The winners of the war, the Allies, met to decide on formal peace terms at the Paris Peace Conference. 

• The League of Nations was approved and started operations, but the United States never joined. On 10 January 1920, the League of Nations formally came into being when the Covenant of the League of Nations, ratified by 42 nations in 1919, took effect. The League Council acted as an executive body directing the Assembly's business. It began with four permanent members—the United Kingdom, France, Italy, and Japan.

• After some limited successes and failures during the 1920s, the League proved ineffective in the 1930s, as it failed to act against the Japanese invasion of Manchuria in 1933. Forty nations voted for Japan to withdraw from Manchuria but Japan voted against it and walked out of the League instead of withdrawing from Manchuria. 

• It also failed to act against the Second Italo-Ethiopian War, after the appeal for international intervention by Ethiopian Emperor Haile Selassie I at Geneva in 1936 went with no avail, including when calls for economic sanctions against Italy failed. Italy and other nations left the League. 

• When war broke out in 1939, the League effectively closed down. 

Declarations by the Allies of World War II (1941–1944) 

• The first step towards the establishment of the United Nations was the Inter-Allied Conference in London that led to the Declaration of St James's Palace on 12 June 1941.

•  By August 1941, American President Franklin Roosevelt and British Prime Minister Winston Churchill had drafted the Atlantic Charter; which defined goals for the post-war world. At the subsequent meeting of the Inter-Allied Council in London on 24 September 1941, the eight governments in exile of countries under Axis occupation, together with the Soviet Union and representatives of the Free French Forces, unanimously adopted adherence to the common principles of policy set forth by Britain and the United States. 

• Roosevelt and Churchill met at the White House in December 1941 for the Arcadia Conference. Roosevelt is considered a founder of the UN, and coined the term United Nations to describe the Allied countries. Churchill accepted it, noting its use by Lord Byron. 

• The text of the Declaration by United Nations was drafted on 29 December 1941, by Roosevelt, Churchill, and Harry Hopkins. It incorporated Soviet suggestions but included no role for France. One major change from the Atlantic Charter was the addition of a provision for religious freedom, which Stalin approved after Roosevelt insisted. 

• Roosevelt's idea of the "Four Powers", refers to the four major Allied countries, the United States, the United Kingdom, the Soviet Union, and China, emerged in the Declaration by the United Nations. 

• On New Year's Day 1942, Roosevelt, Churchill, the Soviet Union's former Foreign Minister Maxim Litvinov, and the Chinese Premier T. V. Soong signed the "Declaration by United Nations", and the next day the representatives of twenty-two other nations added their signatures. During the war, the United Nations became the official term for the Allies. In order to join, countries had to sign the Declaration and declare war on the Axis powers.

• The October 1943 Moscow Conference resulted in the Moscow Declarations, including the Four Power Declaration on General Security which aimed for the creation "at the earliest possible date of a general international organization". 

• This was the first public announcement that a new international organization was being contemplated to replace the League of Nations. 

• The Tehran Conference followed shortly afterwards at which Roosevelt, Churchill and Joseph Stalin, the leader of the Soviet Union, met and discussed the idea of a post-war international organization 

• The new international organisation was formulated and negotiated amongst the delegations from the Allied Big Four at the Dumbarton Oaks Conference from 21 September to 7 October 1944. 

• They agreed on proposals for the aims, structure and functioning of the new organization. It took the conference at Yalta in February 1945, and further negotiations with the Soviet Union, before all the issues were resolved.