The country, whose president, Woodrow Wilson, had dreamt up the idea of the League – America – refused to join it. As America was the world’s most powerful nation, this was a serious blow to the prestige of the League. However, America’s refusal to join the League, fitted in with her desire to have an isolationist policy throughout the world.
Germany was not allowed to join the League in 1919. As Germany had started the war, according to the Treaty of Versailles, one of her punishments was that she was not considered to be a member of the international community and, therefore, she was not invited to join. This was a great blow to Germany but it also meant that the League could not use whatever strength Germany had to support its campaign against aggressor nations.
Russia was also not allowed to join as in 1917, she had a communist government that generated fear in western Europe, and in 1918, the Russian royal family – the Romanovs – was murdered. Such a country could not be allowed to take its place in the League.
Therefore, three of the world’s most powerful nations (potentially for Russia and Germany) played no part in supporting the League. The two most powerful members were Britain and France – both had suffered financially and militarily during the war – and neither was enthusiastic to get involved in disputes that did not affect western Europe.
Therefore, the League had a fine ideal – to end war for good. However, if an aggressor nation was determined enough to ignore the League’s verbal warnings, all the League could do was enforce economic sanctions and hope that these worked as it had no chance or enforcing its decisions using military might.