War crimes in Manchukuo War crimes in Manchukuo were committed during the rule of the Empire of Japan in northeast China , either directly , or through its puppet state of Manchukuo , from 1931 to 1945 . Various war crimes have been alleged , but have received comparatively little historical attention . Legal basis . Although the Empire of Japan did not sign the Geneva Convention s , which have provided the standard definition of war crimes since 1864 , the crimes committed fall under other aspects of international and Japanese law . For example , many of the alleged crimes committed by Japanese personnel broke Japanese military law , and were not subject to court martial , as required by that law . Japan also violated signed international agreements , including provisions of the Treaty of Versailles such as a ban on the use of chemical weapons , and the Hague Conventions ( 1899 and 1907 ) , which protect prisoners of war ( POWs ) . The Japanese government also signed the Kellogg - Briand Pact ( 1929 ) , thereby rendering its actions in 1937 - 45 liable to charges of crimes against peace , a charge that was introduced at the Tokyo Trials to prosecute " Class A " war criminals . " Class B " war criminals were those found guilty of war crimes " per se " , and " Class C " war criminals were those guilty of crimes against humanity . The Japanese government also accepted the terms set by the Potsdam Declaration ( 1945 ) after the end of the war . The declaration alluded , in Article 10 , to two kinds of war crime : one was the violation of international laws , such as the abuse of prisoners of war ; the other was obstructing " democratic tendencies among the Japanese people " and civil liberties within Japan . In Japan , the term " Japanese war crimes " generally only refers to cases tried by the International Military Tribunal for the Far East , also known as the " Tokyo Trials " , following the end of the Pacific War . However , the tribunal did not prosecute war crimes allegations involving mid - ranking officers or more junior personnel . Those were dealt with separately in trials held in China and in the Soviet Union after the surrender of Japan . Revisionist historians have contested that such crimes occurred . Right - wing nationalist groups in Japan dismiss some of the alleged war crimes as lies , or anti - Japanese propaganda , made or being made by the People ' s Republic of China to justify its occupation of Manchuria , and to place modern Japan in a negative light for modern political and foreign policy purposes . Crimes . Human experimentation . Special Japanese military units conducted experiments on civilians and POWs in Manchukuo . One of the most infamous was Unit 731 . Victims were subjected to vivisection without anesthesia , and were used to test biological weapons , among other experiments . According to GlobalSecurity . org , the experiments carried out by Unit 731 alone caused 3 , 000 deaths . Chemical and biological weapons . According to historians Yoshiaki Yoshimi and Seiya Matsuno , Emperor Hirohito authorized the use of chemical weapons in China . Furthermore , " tens of thousands , and perhaps as many 200 , 000 , Chinese died of bubonic plague , cholera , anthrax and other diseases . . . " , resulting from the use of biological warfare . Although there is no record of chemical or biological weapons in Manchukuo itself , these weapons of mass destruction were partly researched , produced , and stockpiled in Manchukuo by the Kwangtung Army . Forced labor . The Japanese military ' s use of forced labor also caused many deaths . According to a joint study of historians Zhifen Ju , Mitsuyochi Himeta , Toru Kubo and Mark Peattie , more than 10 million Chinese civilians were mobilized for forced labor in Manchukuo under the supervision of the Kōa - in . Forced laborers were often assigned work in dangerous conditions without adequate safety precautions . The world ' s deadliest mine disaster , at Benxihu Colliery , occurred in Manchukuo . Drug trafficking . In 2007 , an article by Reiji Yoshida in the Japan Times argued that the Japanese investments in Manchukuo were partly financed by selling drugs . According to the article , a document claimed to have been found by Yoshida directly implicated the Kōa - in in providing funds to drug dealers in China for the benefit of the puppet governments of Manchukuo , Nanjing and Mongolia . This document corroborates evidence analyzed earlier by the Tokyo tribunal which stated that War crimes trials . Khabarovsk War Crime Trial . In late 1949 , numerous members of the former Kwantung Army who had been captured in the Soviet invasion of Manchuria were convicted in connection with the activities of Unit 731 , and related units for their connections with crimes against humanity and the use of chemical and biological weapons . Tokyo Trials . The International Military Tribunal for the Far East convicted a number of high Japanese officials in connection with the invasion of Manchuria , establishment of Manchukuo and with conspiracy to wage aggressive war against China . Those sentenced to death with strong connections to Manchukuo included senior officers in the Kwantung Army Hideki Tōjō , Akira Mutō , Seishirō Itagaki and Kenji Doihara .