Unit 731 is a shorthand term used to refer to the top-secret biological and chemical warfare research facility established by the Imperial Japanese Army in 1935 in the city of Harbin, China. The unit was notorious for conducting brutal and inhumane experiments on prisoners of war and civilians during the Second Sino-Japanese War and World War II, with the aim of developing weapons for use in biological warfare. The experiments carried out by Unit 731 are widely considered war crimes and are a stain on the history of Japan and the world.

Unit 731

Unit 731 was a top-secret biological and chemical warfare research facility established by the Imperial Japanese Army in 1935. It was located in the Pingfang district of the city of Harbin in northeastern China and was notorious for conducting brutal experiments on prisoners of war and civilians during the Second Sino-Japanese War and World War II. The experiments were carried out without the consent of the subjects and often resulted in injury or death.

The unit was involved in research on bubonic plague, cholera, and other diseases, with the aim of developing weapons for use in biological warfare. It is estimated that thousands of people, including Chinese, Korean, and Russian prisoners of war, were subjected to horrific experiments and medical procedures. Some were purposely infected with diseases, others were subjected to vivisection (the dissection of live animals), and still others were frozen to death or subjected to other forms of torture.

After the war, the Japanese government and military officials responsible for the unit’s activities were never held accountable for their crimes. The United States, which occupied Japan after the war, granted immunity to many of the unit’s members in exchange for access to their research, which was considered valuable for the development of its own biological weapons program.

The horrific experiments carried out by Unit 731 are widely regarded as war crimes and are a stain on the history of Japan and the world. Despite the passing of several decades, the legacy of Unit 731 continues to elicit outrage and calls for justice.

Formation

In the 1930s, Japan initiated a secret program to develop biological weapons, due to their belief that the ban imposed by the Geneva Convention of 1925 verified the effectiveness of biological weapons as a tool of warfare. They saw the occupation of Manchuria as an opportunity to carry out this research, as it would provide them with easy access to human subjects for experimentation and isolate the research station from the mainland.

At the helm of this program was Surgeon General Shirō Ishii, who was placed in charge of the Army Epidemic Prevention Research Laboratory (AEPRL) in 1932. Ishii led the establishment of the “Tōgō Unit”, a covert group dedicated to chemical and biological research in Manchuria. The group’s research was driven by Ishii’s belief that Western nations were already investing in similar programs and his desire for Japan to be a leader in this field.

One of Ishii’s key supporters within the army was Colonel Chikahiko Koizumi, who later served as the Health Minister of Japan from 1941 to 1945. Koizumi was a part of a secret committee researching poison gas during World War I, and was inspired by Germany’s successful use of chlorine gas in the Second Battle of Ypres.

The majority of the human subjects used in the experiments carried out by the Tōgō Unit were Chinese, but individuals of various nationalities were also subjected to the inhumane treatment. The research carried out by Japan’s biological weapons program is considered a dark chapter in the country’s history and a gross violation of human rights.

Zhongma Fortress

Unit Tōgō was established at the Zhongma Fortress, a brutal prison and experimentation camp located in Beiyinhe, a village situated 62 miles south of Harbin along the South Manchuria Railway. The prisoners brought to the fortress included a diverse group, ranging from common criminals, captured bandits, anti-Japanese activists, to political prisoners and those arbitrarily arrested by the Kempeitai. Despite the horrors they were about to face, the prisoners were initially kept in good health through a nutritious diet of rice, wheat, meat, fish, and even occasional alcohol.

However, over time, they were subjected to inhumane treatments, including being slowly drained of blood and deprived of food and water. Their deteriorating health was documented, and some were even subjected to vivisection. Others were intentionally infected with deadly diseases such as the bubonic plague.

In 1934, a prison break occurred, posing a threat to the facility’s secrecy, and an explosion took place in 1935, believed to be the result of sabotage. In light of these events, Ishii shut down Zhongma Fortress and received permission to move to Pingfang, located 15 miles south of Harbin, to establish a much larger and more secure facility for his sinister experiments.

Unit 731

In 1936, the expansion of Unit Tōgō was authorized by Emperor Hirohito through a royal decree. The unit was integrated into the Kwantung Army as the Epidemic Prevention Department, and was divided into two distinct units: the Ishii Unit and the Wakamatsu Unit. With a base in Hsinking, these two units operated collectively as the Epidemic Prevention and Water Purification Department of the Kwantung Army, and were commonly referred to as “Unit 731.”

Prince Mikasa, the younger brother of Emperor Hirohito, paid a visit to the Unit 731 headquarters in China and documented his experiences in his memoirs. He described watching films that depicted Chinese prisoners being forced to participate in poisonous gas experiments on the Manchurian plains. The disturbing nature of these experiments, conducted on human subjects, highlights the ruthless and inhumane tactics employed by the unit in pursuit of their biological weapons program.

Other units

In 1936, Emperor Hirohito authorized the growth of Unit 731 and its integration into the Kwantung Army as the Epidemic Prevention Department. It was separated into two units, the “Ishii Unit” and “Wakamatsu Unit”, stationed in Hsinking. From 1940 onwards, the units were collectively referred to as the “Epidemic Prevention and Water Purification Department of the Kwantung Army” or simply “Unit 731”. Prince Mikasa, the Emperor’s younger brother, even visited the Unit 731 headquarters and recorded watching films that showed the cruel experiments performed on Chinese prisoners.

Apart from Unit 731, the Emperor’s decree also led to the establishment of a biological warfare development unit named the Kwantung Army Military Horse Epidemic Prevention Workshop (later known as Manchuria Unit 100) and a chemical warfare development unit referred to as the Kwantung Army Technical Testing Department (later referred to as Manchuria Unit 516). Following the Japanese invasion of China in 1937, additional chemical and biological warfare units were established in major Chinese cities, called the Epidemic Prevention and Water Supply Units. These detachments included Unit 1855 in Beijing, Unit Ei 1644 in Nanjing, Unit 8604 in Guangzhou, and later Unit 9420 in Singapore. These units comprised Ishii’s network and by 1939, it was overseeing over 10,000 personnel. The opportunity to conduct human experiments and the financial support provided by the Japanese army attracted many medical doctors and professors to join Unit 731.

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