Masanobu Tsuji (1900?-1968?) was a colonel and senior staff officer in the World War Two in the Pacific, with immense political power despite his apparently low rank. Tsuji, claiming the authority of Imperial General Headquarters, is believed to have ordered a wide range of atrocities including killings of Australian and Indian prisoners after the fall of Singapore, and of Filipinos and Americans on the Bataan Death March. Field Marshal Count Hisaichi Terauchi supported Tsuji, and was angered when the Japanese commander in the Philippines, Nasaharu Homma, tried to moderate his activities. 
CIA documents declassified in 2006 explain why one of the most notorious Japanese war criminals was never indicted or even held. Seizo Arisue, the last wartime chief of Japanese Army intelligence, who worked with U.S. occupation forces, recruited him into clandestine U.S. service.
Tsuji wrote he was born in 1900, although others have suggested 1903. Ishikawa Prefecture on October 11, 1900, according to his own account, though others have placed his birthdate in 1903. After the Military Academy, he was assigned to the Army General Staff May 1921, then Staff College November in 1924; attended War College circa 1930; reported to have quarreled with faculty; may have met Prince Chichibu, the Emperor's younger brother. 
Second World War
Operational planningTsuji wrote that while there had been extensive planning for the war in China, the decision to go to war in the Southeast Asia and westward -- the "Strike-South" strategy -- was only made in 1941.
It was the duty of the unit to report on all these matters to General Headquarters
in Tokyo. Furthermore the scope of research extended over the whole of the Pacific war regions as well as Malaya, the Philippine Islands, Indonesia, and Burma. Funds apportioned to the unit for research totalled barely 20,000 yen. Even among the commissioned officers chosen for the staff there was not one who had any real experience of the tropics. What is more, in the eyes of those at General Headquarters nearly all the members of the staff were persons to beignored, or held in contempt, or kept at a respectful distance.
Tsuji's unit did the operational planning, based on three assumptions:
- Singapore Fortress was solid and strong facing the sea, but vulnerable on the peninsular side facing the Johore Strait;
- Newspaper reports of a strong Royal Air Force (RAF) presence were propaganda;
- Although British forces in Malaya numbered from five to six divisions (well over 80,000 men), less than half were Europeans.
Under the guise of preemptory attack against possible Chinese Communist guerillas, he drafted the orders to kill somewhere between 3,000 and 10,000 Chinese residents of Singapore. This fact clearly demonstrates he was both predisposed to and fully capable of initiating the most unspeakable of atrocities when he felt they suited his purposes. Even though the killing went on for nearly a month, Yamashita and his staff only learned of Tsuji’s actions well after the fact since the 25th army had been moved to Sumatra leaving only an occupation force in Singapore. 
As the Malaya-Singapore operation progressed, Tsuji differed increasingly with Yamashita. Tsuji wanted a single main thrust at Singapore, while Yamashita wanted flanking movements through "impassable" territory, coupled with small amphibious diversions. It was Tsuji that believed the single thrust would save Japanese lives, while Yamashita considered it most important to keep the British off balance. Tsuji reported these difference to Tojo, long Yamashita's rival, and to Prince Mikasa, hurting Yamashita's reputation with the Emperor.
Yamashita was posted directly back to Manchuria, had no victor's reception, and his proposal for an immediate invasion of Australia was rejected. 
He then moved to the Philippines, a protege of Marshal Sugiyama, who disliked Marshal Homma, the Philippines commander at the start of the invasion.
"U.S. officials also investigated the possibility that, late in the war, the Japanese Army expropriated three tons of gold from French Indochina with the idea that it would be used at a later date to finance the resurgence of the Japanese military establishment. Reports indicated that Tsuji, who spent a great deal of time in Southeast Asia, had distributed part of this haul to his officers and told them to hide it away from Allied hands."
Before his rehabilitation, he was involved in G-2 planning of covert activities to assist the Chinese Nationalists against the Peoples Republic of China.  Note that direct confrontation with China, even through Chiang Kai-shek as a proxy, was against Truman Administration policy, a conflict that led to MacArthur's (and Willoughby's) dismissal.
By 1950, when there were no charges outstanding against Tsuji, Arisue asked him to expand Japanese intelligence operations into Southeast Asia. Tsuji had met many of the former Imperial Japanese Army officers associated with this operation while he was in Singapore. CIA documents released through the IWG explained the puzzlement of many Japanese, who wondered why Tsuji was never charged for crimes sometimes worse that led to the gallows for others. Even after his release, he remained a "person of interest", but was not found to be interrogated. "He avoided capture first by hiding in Southeast Asia, later sheltered by Chiang Kai-shek on mainland China, then secretly in Japan, including as a guest of Kodama. When the United States dropped its war crimes charges against him in 1950, he returned to the public scene, publishing two books about his wartime and postwar experiences that quickly became best sellers."  Many of the other officers would not work with Tsuji and lobbied successfully to have Arisue replace him with former Shanghai kenpeitai Chief Tomita Bunichi. 
Through Hattori, Tsuji became involved in planning one of Willoughby’s most ambitious operations, a Chinese Nationalist invasion of mainland China. In January 1951, G-2 began toying with the notion of encouraging Chiang Kai-shek’s forces to invade south China and establish contact with Chinese anti-communist resistance forces. Willoughby’s subordinates approached Hattori and requested that he and Tsuji prepare the operational details of such a plan. Hattori, whom the CIA believed was a key figure in getting the war crimes charges against Tsuji dropped, now sought to put Tsuji’s military expertise to work for G-2. Planning proceeded through early March, with Tsuji taking the lead.
From the CIA’s perspective, Willoughby put undue trust in both Hattori and Tsuji. Tsuji, who had himself become enmeshed in rearmament plans, purportedly stated in 1951 that it was necessary to “deceive the ally prior to the enemy.” The agency’s analysts also saw “a serious danger that American military personnel in G-2, GHQ will be taken in by [Hattori’s group].” In any event, the planning came to very little, as Willoughby learned in March 1951 that news of the preparations leaked to the Communist Chinese, and the idea was shelved. 
By 1952, Tsuji and Hattori decided that cooperation with the Americans was the best way to rapidly rearm Japan, a position unpopular with many other ex-officers. Backed by Kodama and others, they disagreed with Prime Minister Yoshida Shigeru’s policy of exclusively relying on U.S. military protection instead of rebuilding Japan’s own army. ...In July 1952, Hattori hatched a plot to conduct a coup by murdering Yoshida and replacing him either with the more sympathetic Hatoyama Ichiro or Ogata Taketora. While Tsuji initially supported a coup, Tsuji convinced Hattori to hold off his coup d’etat as long as the conservatives (of the ironically named Liberal Party) were in power. In other words, SCAP's staunchest political ally in Japan was protected by one of Japan’s most well-known alleged war criminals. Nevertheless, the group did consider murdering other government figures to send a message to Yoshida . Hatoyama succeeded in deposing Yoshida in 1954, but it is unclear what role, if any, Hattori and Tsuji played in this.
Member of the Diet
In 1952, Tsuji was elected to the Diet and began a flamboyant career in politics, until his mysterious disappearance in 1961 during travel in Southeast Asia.
His son, Takeshi, was eight days from being admitted to the University of Tokyo in April 1961. Kenshiro Seki, president of a famous Japanese inn called Sekiya, to which the elder Tsuji would go for relaxation, said that he had told Seki and his wife, "I'm going to Laos on orders from Prime Minister (Hayato) Ikeda." Seki "speculated in an interview with Kyodo News that his father felt he had fulfilled his parental responsibility because his son had passed the rigorous university entrance exam and would be capable of supporting himself after graduation."
- Patti, Archimedes L. A (1980). Why Viet Nam?: Prelude to America's Albatross. University of California Press. , p. 494
- Petersen, Michael (2006), Chapter 8: The Intelligence that Wasn't: CIA Name Files, the U.S. Army, and Intelligence Gathering in Occupied Japan, Researching Japanese War Crimes Records, National Archives and Records Administration Interagency Working Group (IWG)
- Dan Ford (1994 notes), Colonel Masanobu Tsuji, the infamous Japanese master spy
- Tsuji, Masanobu, Singapore 1941-1942: The Japanese Version of the Malayan Campaign of World War II (1988), p.13, quoted in, "The Fall of Fortress Singapore: Churchill's Role and the Conflicting Interpretations", Rab Peterson, Sophia International Review 
- Alan C. Headrick (8 February 1994), Bicycle Blitzkrieg: The Malayan Campaign and the Fall of Singapore, U.S. Naval War College
- Jim Nelson, The Causes of the Bataan Death March Revisited, U.S.-Japan Dialogue on POWs
- Bergamini, pp. 872-873
- Tim Weiner (2007), Chapter 12: We Ran It in a Different Way, Legacy of Ashes: The History of the CIA, Doubleday
- Shiro Yoneyama (26 July 2000), "Disappearance of Masanobu Tsuji remains a mystery", Japan Times