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Ken Yuasa (Japanese: 湯浅 謙) (October 23, 1915 – November 2, 2010) was a World War II surgeon for the Japanese army. During his service in occupied China, he (along with at least 1000 other doctors and nurses) conducted vivisections on Chinese prisoners and civilians, and provided typhoid and dysentery bacillus to the Japanese army for use in biological warfare. Years after the war, he began to realize the extent of the atrocities he and others had committed and began writing and speaking about his experiences all over Japan.
Yuasa was born in Saitama prefecture and grew up in Tokyo, Kyobashi district. He decided to follow his father's example and, after graduating from Jikei University's School of Medicine in March, 1941, became a doctor. He had originally hoped to become a rural practitioner traveling to remote villages that had no doctor and helping to treat underprivileged patients. However, along with the vast majority of able-bodied young men in Japan, he was soon drafted into the Imperial Army.
Within six weeks into the beginning of his service in China, Yuasa was conducting vivisections of prisoners. The Japanese army believed in the importance of performing operations on live prisoners as a way of learning how to better care for Japanese casualties. Yuasa's first vivisection was in March 1942 in the army hospital in Changzhi (formerly Luan) in Shanxi Province. Two Chinese prisoners—a younger man and an older man—were handcuffed to operating tables while 20 other doctors and nurses observed. First, an appendectomy was performed on one of the conscious patients, after which the doctor sutured the wound, and then a tracheotomy. Impelled by interest, Yuasa went on to perform an amputation of the right arm of one of the prisoners. Yuasa  being afraid during the course of this vivisection, but by his third trial, he  to being a willing participant. He  an additional incident when he operated on a Chinese prisoner who had been deliberately shot so he could be operated on as practice for a "real situation". He was under orders not to use anesthesia. Yuasa has said that in all he participated in 6 such vivisections.
After the war ended, Yuasa became a prisoner of war in China. He was compelled by his captors to record on paper all of the atrocities he had committed as a doctor in China. It was not until he began to write down in detail his past actions, that he began to portray himself as having realized the magnitude of what he had committed. In 1956, he was released and allowed to return to Japan.
Hoping to act as a reminder to Japan that these atrocities must never be repeated, Yuasa was one of a handful of doctors who eventually stepped forward to confess their crimes to the Japanese public and the world at large. He publicly detailed the army's atrocities since his return to Japan in the 1950s. He received death threats from various individuals and was advised by former colleagues at the Luan army hospital to "go easy" on his revelations. Until his death, Yuasa continued touring Japan, and telling audiences of his wartime experiences.
- Jun Hongo (2007-10-24). "Vivisectionist recalls his day of reckoning". Japan Times. p. 3.