Japan and the US both practiced isolationism for different reason. The Japanese sought to invade all of Asia and wanted no parts of global sancations imposed by the League of Nations. The US considered the effects of WWI and were still reeling from the Depression; the political sentiment went back to George Washington who believed the US should stay out of international conflict

It is interesting to note the genesis of Chinese Communism which really occurred began as a political means to combat the invasion of China. Government Nationalistic policies and the scorched-earth policy to stop Japan encroachment failed. The people of China were prime for the establishment of a new order.

After the League of Nations determined that Japan was responsible for Manchuria, and mandated the return of the territory, Japan left the League of Nations. The Stimson Doctrine basically stated LON refusal to officially recognize statehood in the land taken by Japan force.

Japan owned this railroad lcoated in a Chinese province. The Japanese would go to the lenghts of bombing their own property, also risking lives to aggress against Chinese territory. Japan took advantage of China's weaken military and invaded Manchuria, which became known as Manchunkuo.