A Pan-Asianist, Tsuji pressured Asian countries to support Japan in World War II, despite being involved in atrocities such as the Bataan Death March and Sook Ching.

He was a leading proponent of the concept of gekokujō, (literally "the bottom overthrowing the top") by acting without or contrary to authorization.

In March 1939, after the Japanese defeat at the hands of the Soviets at Changkufeng, Tsuji instigated an aggressive border policy, which triggered the Nomonhan Incident.

[8] When the war against America and Britain started, Tsuji was on the staff of General Tomoyuki Yamashita, whose army invaded Malaya.

[10] After the capture of Singapore, Tsuji helped plan the Sook Ching, a systematic massacre of thousands of Malayan Chinese who might be hostile to Japan.

His aggressive and insubordinate attitude exacerbated the Soviet–Japanese border conflicts, and helped incite the Battle of Khalkhin Gol in 1939.

He was an energetic and efficient planner, if notoriously arrogant, and once helped quell panic in the ranks by ostentatiously having a bath under fire in the front lines.

[citation needed] When the Japanese position in Burma collapsed in 1945, Tsuji escaped, first to Thailand and then to China, where he renewed the contacts made in Nanking.

He began publishing books and articles about his war experiences, including an account of the Japanese victory in Malaya.

The documents described Tsuji to be an "inseparable pair" with Takushiro Hattori and stated them to be "extremely irresponsible" and that they "will not take the consequences for their actions."

Additionally, Tsuji was stated to be "the type of man who given the chance, would start World War III without any misgivings."

[17][18][19] Additionally, the files contain information that Hattori had allegedly planned a coup to overthrow the Japanese government in 1952 that involved the assassination of Prime Minister Shigeru Yoshida and replacing him with Ichiro Hatoyama of the DPJ, but Tsuji prevented the coup by persuading the group that the real enemies were not conservatives like Yoshida but the Socialist Party.

However, the files also state that the CIA learned about the attempt only after the fact and that the information was gained from an unreliable source from China.

Some academics such as the media theorist and Americanist[20] Tetsuo Arima of Waseda University have suggested that the entire story might have been a bluff leaked to the Chinese by Tsuji himself as a way to make him seem more influential than he actually was.

[18][19][21][22][23] According to the CIA files, when Tsuji returned to Vientiane from Hanoi, he was kidnapped by the Chinese Communist Party and was being imprisoned in Yunnan, ostensibly to be used in some way to worsen Japanese-American relations or Japan's standing in Southeast Asia.