A recently discovered Japanese document has revealed details of Japan’s biological warfare during the second Chinese-Japanese war and World War Two.

Japan’s Unit 731 was at the center of atrocities, such as biological experiments conducted on living people.

Written in 1943 by a Japanese army surgeon, the document expliains that Japan used biological weapons six times over two years from 1940, infecting a total of 26-thousand people.

A Japanese civic organization found the document at the Kansai-kan of Japan’s National Diet Library in Kyoto. It details the dates and methods of Unit 731’s biological warfare operations and the number of victims.

The Japanese government has been denying the human experiment allegations, although materials proving the unit’s atrocities have surfaced.