A public document has recently come to light that shows the U.S. military ordered Occupation authorities to censor the mail of former members of Unit 731, the Imperial Japanese Army section that conducted bacterial warfare experiments on people, a Tokyo-based historian said.
The document, stamped “secret,” was discovered by Taketoshi Yamamoto, a professor of media history at Waseda University in Tokyo, from a microfilm archive at the National Diet Library.
The document was sent from the U.S. Army to the private censorship bureau of the U.S.-led Occupation authority on Feb. 15, 1946.
The document lists the names and addresses of 12 Japanese whose mail should be censored, including former Unit 731 commander Lt. Gen. Shiro Ishii and Kanji Ishihara, a former army officer who plotted the Manchurian Incident in 1931.
It also lists the names of nine other former Unit 731 members with medical backgrounds whose address were not known to the authority. They had worked at facilities of the notorious unit.
According to Yamamoto, the U.S. military granted immunity to former Unit 731 members in exchange for receiving data on bacterial warfare, including information on live experiments.
“Censorship may have been needed for the U.S. to give the immunity to Unit 731, checking if they were planning any retaliation against the U.S. or not,” Yamamoto said.
“Few lists of people (that Occupation authorities) watched (for security reasons) are left today. This is precious material, which shows the U.S. secretly conducted censorship,” he said.
A message ordering the document’s destruction can still be read on a corner of the paper.
Unit 731, launched in 1936, was based in the outskirts of Harbin, northeastern China.
The unit secretly studied and developed bacterial weapons by conducting tests on Chinese and Russian prisoners.
The number of victims is believed to exceed 3,000.
Unit 731 spread the pest bacillus during the war with China and planned in vain to stage an attack against the U.S. during the closing days of World War II.
After the war, the unit blew up most of its facilities in a bid to destroy evidence of its weapons and experiments.