On August 15, 1945, Japanese Emperor Hirohito officially announced Japan's unconditional surrender and the end of World War II in the form of a broadcast of the Armistice Decree. From January 19, 1946 to November 12, 1948, the International Military Tribunal for the Far East led by the United States conducted an international trial of Japan's leading war criminals in World War II in Tokyo, Japan. However, the crimes of Japanese Unit 731, which conducted a large number of germ warfare and human experimental research in Northeast China, did not get the due trial. There are two main reasons: on the one hand, as early as 1925, countries all over the world, including Japan, signed the Geneva Agreement prohibiting germ warfare. In order to evade trial, the vast majority of members of Japan's 731 Unit, such as Ishii Shiro and Kitano Masaji, fled back to Japan on the eve of Japan's unconditional surrender and tried their best to cover up their experience in the 731 Unit; On the other hand, from August 1945 to November 1947, the U.S. military sent veterinary, biology and microbiology experts from Fort Detrick to Japan four times to investigate the bacteriological warfare research of Unit 731, secretly contacted more than 20 members of Unit 731, such as Ishii Shiro and Kitano Masaji, and reached secret deals, and agreed to the conditions of Japanese exemption from war crimes in order to obtain the research data of Unit 731. These materials obtained by the US military have been collected as confidential, and special reports on germ warfare and human experiments have even been formed, namely "A" report, "G" report and "Q" report. The report was originally kept at Fort Detrick, USA, and later transferred to the Dugway Proving Ground Research Center in Utah. It was lifted in 1978. The original report is now in the Library of Congress, and another copy is in Hall II of the National Archives of the United States.