What organization was the forerunner of the UN?

The League of Nations served as the forerunner of the United Nations. Established after World War I in 1920, the League aimed to promote peace and cooperation among countries in the hopes of preventing another global conflict. It was conceived during the Paris Peace Conference and was the first international organization of its kind to provide a platform for dialogue and resolution of international disputes. Unfortunately, the League ultimately failed to prevent World War II, leading to the recognition of the need for a more robust and effective international organization, which resulted in the formation of the United Nations in 1945.

Other organizations mentioned, such as the European Union and NATO, were formed later and serve different functions primarily related to economic cooperation and military alliance, respectively. The Commonwealth of Nations is a political association of member states, most of which are former territories of the British Empire, focusing on promoting democracy and development, rather than serving as a precursor to the UN's global peacekeeping and diplomatic roles.