Manchuria was 1931.
So it just slowed them?
For a number of years before outright invading, the Japanese were aggressively pushing heroine on the Chinese, who were not allowed to carry weapons while enforcing Chinese laws against heroine, due to some kakamamee treaty they were forced to sing. See Moment in Peking by Lin YuTang. Whole book is engrossing, and I can’t recall the exact chapter.