His relationship with Kawashima soured after a fictionalized account of her exploits was published in Japan which mentioned him by name and after he found that her movements were being closely monitored by KMT agents.

From 1937 to 1939, Tanaka was commander of the IJA 25th Mountain Artillery Regiment in Manchukuo, which was at the disastrous Battle of Lake Khasan against the Soviet Union.

[2][page needed] At the end of 1940, Tanaka was recalled back to Japan, and the following year became Commandant of the Nakano School, the primary espionage and sabotage training facility for the Japanese army.

[3] Suffering from poor health, Tanaka went into the reserves until September 1942 when he was attached to the Eastern Defense Army; however, he was hospitalized from October due to acute depression, and retired from military service in March 1943.

He was used by chief prosecutor Joseph Keenan to persuade Hideki Tōjō to revise his testimony referring to Emperor Hirohito's ultimate authority.