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 Conventions, 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.

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.

Human rights violations

 * Arrest of civilians without due cause by the local Manchukuo police or Japanese authorities.
 * Torture of prisoners in regular penal or military jails.
 * Disappearances and Extrajudicial execution of political opponents
 * Preferential civil rights for Japanese subjects over other nationalities.
 * Forced land appropriations either with or without legal orders in favour of Japanese citizens or private and government companies.
 * Use of criminal gangs for robbery and intimidation of political opposition

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 Japan's real purpose in engaging drug traffic was far more sinister than even the debauchery of Chinese people. Japan, having signed and ratified the opium conventions, was bound not to engage in drug traffic, but she found in the alleged but false independence of Manchukuo a convenient opportunity to carry on a worldwide drug traffic and cast the guilt upon that puppet state (...) In 1937, it was pointed out in the League of Nations that 90% of all illicit white drugs in the world were of Japanese origin...

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.