The League of Nations came into being after the end of World War One. The League of Nation’s task was simple – to ensure that war never broke out again. After the turmoil caused by the Versailles Treaty, many looked to the League to bring stability to the world.
America entered World War One in 1917. The country as a whole and the president – Woordrow Wilson in particular – was horrified by the slaughter that had taken place in what was meant to be a civilized part of the world. The only way to avoid a repetition of such a disaster, was to create an international body whose sole purpose was to maintain world peace and which would sort out international disputes as and when they occurred. This would be the task of the League of Nations.
After the devastation of the war, support for such a good idea was great (except in America where isolationism was taking root).