The League of Nations
The predecessor of the United Nations was the League of Nations, established in 1919, after World War I, under the Treaty of Versailles "to promote international cooperation and to achieve peace and security."
Despite some early successes, the League of Nations was not able to prevent World War II.
As of 20 April 1946, the League of Nations ceased to exist, having handed over all of its assets to the United Nations, and having granted the new UN Secretariat full control of its Library and archives.
Earlier international organizations and bodies
In 1865, States first established international organizations to cooperate on specific matters. The International Telecommunication Union was founded in 1865 as the International Telegraph Union, and the Universal Postal Union was established in 1874. Both are now United Nations specialized agencies.
In 1899, the International Peace Conference was held in The Hague to elaborate instruments for settling crises peacefully, preventing wars and codifying rules of warfare. It adopted the Convention for the Pacific Settlement of International Disputes and established the Permanent Court of Arbitration, which began work in 1902.