used to test biological weapons, among other experiments. Between 3,000 and 12,000 men, women, and children died during human experimentation conducted by Unit 731. 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 owing to systematic Japanese destruction of records, 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 Kwantung 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 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