Opposition to The League of Nations Treaty 1920; Flickr Commons 

After WWI, the “war to end all wars”, anti-war sentiment was strong and  President  Woodrow Wilson promoted the idea of the League of Nations to avoid future conflicts. Despite his vigorous support, opposition by Republicans in the U.S. Senate  was fierce, and the USA did not join the League of Nations which was established in October 1919.

The Empire of Japan joined the League in 1933.