Which part of China did japan invade in 1931?

The 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.

In 1931 Japan occupied Manchuria, in the northeastern part of China. Manchuria is a region rich in minerals and raw materials for industries. The Japanese set there a puppet state, Manchukuo, whose formal head was the last Chinese emperor, Puyi, though real control was in Tokyo's hands.