In early 1933 the Japanese already occupied Manchuria and they then invaded northern China and set up a puppet government called Manchukuo. Japan and China still not want a formal declaration of war at this time. The Russians recognized this new government as legitimate to appease the Japanese to try and keep them from invading Russia. The only other countries to recognize this puppet government were the Vatican and El Salvador.

(Book – Mao: The Unknown Story – Jung Chang and Jon Halliday)