In March 1981, Italian financial police searching the home and offices of businessman Licio Gelli uncovered something extraordinary: a list containing the names of hundreds of military officers, intelligence chiefs, politicians, bankers, judges, journalists and business leaders.

Unit 731 was operated by the Imperial Japanese Army’s Kwantung Army under physician and army officer Shiro Ishii. Its principal complex was at Pingfang, outside Harbin, in Japanese-controlled Manchuria. Officially it was disguised as an “Epidemic Prevention and Water Purification Department.” In reality, it became the hub of a much larger network devoted to biological warfare.