It is no exaggeration to say that Unit 731 was the scene of some of the most disturbing and sickening crimes ever committed. During both the Second Sino-Japanese War and the Second World War, the six square kilometer complex served as a Japanese research and development unit for biological and chemical weapons. Research conducted there included human experimentation, which led to the torture and death of over 3,000 men, women and children inside the facility and many more people beyond the unit's walls. Unit 731 was established in 1936 and was located in Pingfang in Manchukuo, which was a Japanese puppet state at that time. Today, it forms part of Northeast China. The facility's commander was General Shir Ishii, the chief medical officer of the Japanese Army and a long-time advocate of the use of biological and chemical weapons. Human experimentation was carried out as part of a project known as 'Maruta'. The test subjects chosen were intentionally varied and included common criminals, war criminals, political prisoners and groups of ordinary citizens rounded up by the Japanese military police. The vast majority, around 70%, were Chinese, while more than one quarter of the prisoners were Russian. Babies, young children, pregnant women and the elderly were all included amongst the victims of the experiments. Of particular interest to the scientists working at Unit 731 was the effects of certain diseases on the human body. These diseases included anthrax, bubonic plague, cholera and typhoid. The research was intended to help Japan to make advances in germ warfare for use against enemy forces and civillians. Many prisoners at the facility, including the children, were infected with these diseases and subjected to gruesome tests and surgeries. Organs were removed from some of the test subjects while they were still alive, in order to assess the effects of diseases on the organs before decomposition set in. These particular experiments included the removal of parts of the brain, liver, lungs and intestines of the victims. Others had their limbs removed to study blood loss and on some occasions, those limbs were reattached to the opposite side of the body, to see how the body would respond. Both men and women were infected with sexually transmitted diseases, including gonorrhea and syphilis. Prisoners were also subjected to flea infestations, with the purpose of gathering huge amounts of disease-carrying fleas for use as a weapon. Away from the field of germ warfare, other weapons were tested on the prisoners, including flamethrowers, grenades and bombs. Some test subjects were placed in gas chambers to assess how long a human could survive in such conditions, while others were injected with the blood of various animals or were buried alive. Research carried out at Unit 731 led directly to the development of bioweapons used against the Chinese population. Purposely discreet weapons, including infected food, infected water, infected clothing and plague-carrying fleas were used against Chinese civillians and led to the deaths of hundreds of thousands. Local authorities were mostly unaware of the horrors taking place at the facility. A cover story was generated and they were informed that Unit 731 was a lumber mill. This story led to a cruel in-joke at the facility, where staff would refer to their test subjects as 'logs'. Human experimentation continued to take place at Unit 731 until the Russians invaded Manchukuo in August 1945. General Shir Ishii immediately ordered for the facility to be destroyed and for the people who worked there to take their secrets to the grave with them. However, the facility survived the destruction attempts and was stormed by allied forces. After Japan surrendered to the allies at the end of the Second World War, Ishii and his men were arrested and interrogated by the Soviet Union. Some of the staff members were eventually tried at the Khabarovsk War Crime Trials. However, many of those who carried out the grotesque experiments did not face justice for their crimes. The Supreme Commander of the Allied Powers, Douglas MacArthur, secretly granted several of them immunity from prosecution in exchange for the results of their research. The United States believed the resulting data could be extremely valuable to their own research into biological and chemical weapons. They concluded that the research could never be otherwise obtained and were also concerned that it might fall into the hands of their post-war superpower rivals, the Soviet Union. The Soviet Union, for their part, also gathered some documentation from the site. As a result, they went on to build a biological weapons facility of their own, in the city of Sverdlovsk. This facility would later be the site of an accidental anthrax leak. Shir Ishii was never tried for his role in the war crimes. Amazingly, some sources suggest that after the war, he even travelled to the United States to advise them on the subject of biological weapons. Other sources dispute this however, and claim he remained in Japan until his death. He eventually died at the age of 67, from throat cancer. Many other researchers and scientists from the facility also escaped justice and went on to enjoy careers in various fields, including medicine, teaching and even politics. The experiments which took place at Unit 731 remain amongst humanity's darkest hours. Today, some sections of the facility remain and have been preserved to function as a museum for war crimes.