Men Behind the Sun

Men Behind the Sun (Chinese: 黑太陽731; lit. 'Black Sun: 731') is a 1988 Hong Kong historical horror film directed by Mou Tun-fei. The movie offers a graphic look at the war crimes carried out by the Empire of Japan at Unit 731, a covert biological weapons research unit of the Imperial Japanese Army during the Second Sino-Japanese War. It was one of the first films in Hong Kong to receive a 'Level III' classification, though that distinction actually belongs to another 1988 release, such as 'The Untold Story' or 'Her Vengeance'.

The story begins with a caption: "Friendship is friendship; history is history." A group of Japanese boys are drafted into the Youth Corps and sent to a Unit 731 facility led by Dr. Shirō Ishii. There, they witness horrific experiments aimed at developing a highly contagious strain of bubonic plague to use as a last-resort weapon against the Chinese. The boys befriend a local mute Chinese boy, playing catch with him. When their commanding officers order them to bring the child to the facility, they naively comply, believing no harm will come to him. Instead, the medical staff vivisects the boy and removes his organs for research. Realizing what happened, the young soldiers stage a minor revolt by physically beating their commanding officer.

Dr. Ishii later develops a prototype ceramic bomb designed to release infectious fleas without killing them upon detonation. To test it, he orders Chinese prisoners tied to crosses, but the experiment fails as Japanese aerial forces retreat. The prisoners break free and try to escape, but Japanese troops hunt them down, killing nearly all of them—including some Japanese soldiers. After learning of the atomic bombings of Hiroshima and Nagasaki and Russia's declaration of war, Dr. Ishii initially orders his subordinates and their families to commit suicide but is persuaded to evacuate them instead, with suicide only if captured. Unit 731 then destroys evidence, gassing remaining test subjects and blowing up the facilities.

That night, as Japanese troops and families wait at a train station to return to Japan, the lone survivor of Unit 731, disguised as a soldier, attacks but is impaled by a Japanese flag. The Youth Corps clutch the blood-stained flag in horror as they depart. Closing passages note that Dr. Ishii cooperated with the Americans, handing over his research and agreeing to work for them.