Who were the key member countries of the League of Nations?
Britain, France, Italy, Japan. These were the permanent members on the Council of the League.
Key countries who were not part of the League when it was created include Germany (1926), the USSR (1934), and the USA (never joined).
Who were the founding member countries of the League of Nations?
Argentina, Australia, Belgium, Bolivia, Brazil, Canada, Chile, China, Columbia, Cuba, Czechoslovakia, Denmark, El Salvador, France, Greece, Guatemala, Haiti, Honduras, India, Italy, Japan, Liberia, the Netherlands, New Zealand, Nicaragua, Norway, Panama, Paraguay, Persia, Peru, Poland, Portugal, Romania, Siam (Thailand), Spain, Sweden, Switzerland, South Africa, the United Kingdom, Uruguay, Venezuela, Yugoslavia.