What led to so much Japanese invasion?

he Japanese invasion of Manchuria began on 18 September 1931, when the Kwantung Army of the Empire of Japan invaded Manchuria immediately following the Mukden Incident. At war’s end in February of 1932, the Japanese established the puppet state of Manchukuo. Their occupation lasted until the success of the Soviet Union and Mongolia with the Manchurian Strategic Offensive Operation in mid-August of 1945.

Explanation:

you can't, there's no way sorry