The film draws on documented evidence of the Japanese army's crimes during the Nanjing Massacre.
The director deliberately casts performers from a variety of regions — southerners, northerners, natives of Nanjing and those from beyond — to reflect Nanjing's status as a cultural crossroads. He encourages them to perform in regional dialects, inspired by his grandparents, who converse seamlessly while retaining their distinct regional accents.
The film is loosely inspired by the uncovering of a crucial piece of evidence from the Nanjing Massacre. In 1938, fifteen-year-old darkroom apprentice Luo Jin secretly assembled photographs of the atrocities, taken by Japanese soldiers, into an album which he concealed. That album was later discovered by Wu Xuan, another Chinese civilian, who safeguarded it for years before handing it to the post‑war authorities.
Director Ao Shen Ao Shen reveals that the film's central inspiration came from the dual meaning of the English word 'shoot' — both "to fire a gun" and "to take a photograph." He explained: 'In war, invading forces use the word "shoot" to conceal atrocities, whereas civilians use it to document the truth. These two acts may appear parallel, but they represent a struggle between life and death.'
The film's portrayal of Japanese soldiers removing bricks from Nanjing's city wall echoes historical accounts that materials were taken for Japan's Hakko Ichiu Tower. The surviving monument incorporates over 370 stones from occupied territories, including more than 200 from China, and research indicates that some of these stones originated in Nanjing.
The postman Su Liuchang's staff number (1213) corresponds to the date on which the Nanjing Massacre began — 13 December 1937.
While filming the group portrait in the photographic studio scene, young actress Enyou Yang (Jin Wanyi) proposed an unscripted character choice to the director. The then ten-year-old argued that her sheltered character — having never directly witnessed Japanese atrocities — would naturally remain playful during the sitting. This input was incorporated into the final cut, where Wanyi's authentic expression contrasts with those of the others.
