Question: What unit was directed by Shiro Ishii and based at the Pingfang district of Harbin?

full_context: Document 1: Naval Medical Research Unit One: Naval Medical Research Unit One was a research laboratory of the US Navy which was founded as Naval Laboratory Research Unit 1, a Naval Reserve Unit at the University of California Berkeley in the life sciences building in 1934 after a campaign by a Berkeley scientist Albert P. Krueger to the Bureau of Medicine and Surgery to have a laboratory to study and prevent influenza and respiratory infections in naval forces. It was mobilized as an active duty naval unit in 1941 to study the epidemiological impact of diseases such as influenza, meningitis, and catarrhal fever, as well as tropical diseases such as malaria on the US Navy during World War II.
Document 2: Mayuri Kurotsuchi: 110 years prior to the series, Mayuri Kurotsuchi was an inmate in the Maggots Nest, the only one dangerous enough to be chained behind bars for his utter lack of regard for the life when it comes to experimentation. But that changed when Mayuri is visited by Kisuke Urahara and his lieutenant Hiyori Sarugaki, the former offering Mayuri a position in the SRDI. After initially refusing being Urahara's assistant, Mayuri accepts when Urahara points out that he be his successor should anything happen to him. Nine years after his release, Kisuke and Hiyori forced to leave the Soul Society, Mayuri becomes the new captain of Squad 12 as the result of the fifth experiment in his life-creating Nemuri Project while later taking the seventh surviving experiment, Nemu Kurotsuchi, to be his lieutenant and lab assistant while pretending to be uncaring towards her to hide his joy of creating a fully stable artificial life form. During this time, Mayuri experimented on Quincies, including Soken Ishida, the grandfather and trainer of Uryū Ishida.
Document 3: Bruce Edwards Ivins: Bruce Edwards Ivins (April 22, 1946 – July 29, 2008) was an American microbiologist, vaccinologist, senior biodefense researcher at the United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Maryland, and the key suspect in the 2001 anthrax attacks.
Document 4: Definitions of Japanese war crimes: There are differences from one country to another regarding the definition of Japanese war crimes. War crimes have been broadly defined as violations of the laws or customs of war, which include crimes against either enemy combatants or enemy non-combatants. War crimes also included deliberate attacks on citizens and property of neutral states as they fall under the category of non-combatants, as at the attack on Pearl Harbor. Military personnel from the Empire of Japan have been accused and/or convicted of committing many such acts during the period of Japanese imperialism from the late 19th to mid-20th centuries. They have been accused of conducting a series of human rights abuses against civilians and prisoners of war (POWs) throughout east Asia and the western Pacific region. These events reached their height during the Second Sino-Japanese War of 1937–45 and the Asian and Pacific campaigns of World War II (1941–45).
Document 5: Yujiro Ishihara: Yujiro Ishihara (石原 裕次郎 , Ishihara Yūjirō , December 28, 1934 – July 17, 1987) was a Japanese actor and singer born in Kobe. His elder brother is Shintaro Ishihara, an author, politician, and the Governor of Tokyo between 1999 and 2012. Yujiro's film debut was the 1956 film "Season of the Sun", based on a novel written by his brother. He was beloved by many fans as a representative youth star in the films of postwar Japan and subsequently as a macho movie hero. He was extravagantly mourned following his early death from liver cancer.
Document 6: Building 257: Building 257, also known as Lab 257, was a United States biological warfare research laboratory located at Fort Terry on Plum Island, New York. Originally intended for munitions storage, the facility researched anti-animal biological agents beginning in 1952 under the United States Army. Biological warfare research continued in the building under the United States Department of Agriculture (USDA) until a new laboratory was completed.
Document 7: Kenji Doihara: Kenji Doihara (土肥原 賢二 , Doihara Kenji , 8 August 1883 – 23 December 1948) was a general in the Imperial Japanese Army in World War II. He was instrumental in the Japanese invasion of Manchuria for which he earned fame taking the nickname 'Lawrence of Manchuria', a reference to Lawrence of Arabia, although according to Jamie Bisher this flattering sobriquet was rather misapplied given that Colonel T.E. Lawrence fought to liberate, not to oppress a people. Furthermore, according to the opinion of his military chief in Manchuria, Lieutenant-General Ishiwara Kanji, his heavy addiction to opium contributed to his unreliability as an army officer.
Document 8: Susumu Ito: He was in auto mechanic school when he was drafted into the military in 1940, two years before the Japanese attack on Pearl Harbor. He worked as a mechanic, but was eventually assigned to the all Japanese-American 442nd Regimental Combat Team, which became the most decorated unit for its size and length of service in the U.S. Army during World War II. He was an artillery spotter (forward field observer) assigned to C Battery. He was promoted to the rank of second lieutenant on October 19, 1944. Ito participated in the famous rescue of the "Lost Battalion", the first battalion of the 141st U.S. Infantry Regiment of the 36th Texas Division. The action took place in the Vosges Mountains, in France, in October 1944. Both units were attached to the Seventh U.S. Army. The Lost Battalion had been cut off and surrounded by the Germans. Lt. Ito was attached to I Company of the 442, which effected the rescue of the Lost Battalion. Though the 442nd suffered extremely heavy casualties in the engagement, Ito emerged unscathed. He was attached to I Company, of which only eight members survived this action. Of the rescue, Ito later recalled, "Looking back, it wasn't an easy outing, but having come through it intact, it was an experience that cannot be forgotten or easily duplicated. At the time, I thought that this was more or less a typical battle encounter with a strong enemy and not a special or unique mission. I guess my analysis is not shared by history." The U.S. Army later declared the Rescue of the Lost Battalion to be one of the top ten battles of the U.S. Army in its history.
Document 9: American cover-up of Japanese war crimes: The American cover-up of Japanese war crimes occurred after the end of World War II, when the occupying US government granted political immunity to military personnel who had engaged in human experimentation and other crimes against humanity, predominantly in mainland China. The pardon of Japanese war criminals, among whom were Unit 731's commanding officers General Shiro Ishii and General Masaji Kitano, was overseen by General of the Army Douglas MacArthur in September 1945. While a series of war tribunals and trials was organized, many of the high-ranking officials and doctors who devised and respectively performed the experiments were pardoned and never brought to justice. As many as 12,000 people, most of them Chinese, died in Unit 731 alone and many more died in other facilities, such as Unit 100 and in field experiments throughout Manchuria.
Document 10: Shuntaro Hida: Shuntaro Hida (1 January 1917 – 20 March 2017) was a Japanese physician who was an eyewitness when the "Little Boy" atomic bomb was dropped on Hiroshima by the "Enola Gay" on 6 August 1945. He treated survivors as a medical doctor and wrote about the effects of radiation on the human body.
Document 11: 267th Chemical Company: The 267th Chemical Company was a military unit of the U.S. Army Chemical Corps responsible for the surety of chemical warfare agents dubbed "RED HAT" deployed to the Islands of Okinawa, Japan and subsequently Johnston Atoll in the Pacific Ocean. A recently discovered Army document reveals that the true mission of the 267th Chemical Company was the operation of the Okinawa deployment site as part Project 112. Project 112 was a 1960s biological warfare field test program that was conducted by the Deseret Test Center. Okinawa is not listed as a test site under Project 112 by the U.S. Department of Defense.
Document 12: Japanese Devils: Japanese Devils (or Riben Guizi 日本鬼子 ) is a Japanese documentary about the war crimes committed by the Imperial Japanese Army between 1931 and 1945. The documentary is a series of interviews with 14 Japanese veterans of the Second Sino-Japanese War who recount rape, massacres, bio-experiments, and cannibalism. The accuracy of these interviews is contested by Japanese nationalist critics.
Document 13: Unit 731: Unit 731 (Japanese: 731部隊 , Hepburn: Nana-san-ichi Butai ) was a covert biological and chemical warfare research and development unit of the Imperial Japanese Army that undertook lethal human experimentation during the Second Sino-Japanese War (1937–1945) of World War II. It was responsible for some of the most notorious war crimes carried out by Japan. Unit 731 was based at the Pingfang district of Harbin, the largest city in the Japanese puppet state of Manchukuo (now Northeast China).
Document 14: United States and weapons of mass destruction: The United States is known to have possessed three types of weapons of mass destruction: nuclear weapons, chemical weapons, and biological weapons. The U.S. is the only country to have used nuclear weapons in combat, when it detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki during World War II. It had secretly developed the earliest form of the atomic weapon during the 1940s under the title "Manhattan Project". The United States pioneered the development of both the nuclear fission and hydrogen bombs (the latter involving nuclear fusion). It was the world's first and only nuclear power for four years (1945–1949), until the Soviet Union managed to produce its own nuclear weapon. The United States has the second largest number of deployed nuclear weapons in the world, after Russia.
Document 15: Shirō Ishii: Surgeon General Shirō Ishii (石井 四郎 , Ishii Shirō , ; June 25, 1892 – October 9, 1959) was a Japanese army medical officer, microbiologist and the director of Unit 731, a biological warfare unit of the Imperial Japanese Army involved in forced and frequently lethal human experimentation during the Second Sino-Japanese War (1937–1945).
ground_truth: Unit 731