Chongqing - Marking 85th anniversary of the "June 5 Tunnel Massacre" , a local picture book author has turned his award-winning illustrated book The Cave into an 11-minute animated short film to keep alive the memory of one of World War II's deadliest civilian tragedies. Liu Heyue, a Chongqing-born illustrator and writer, adapted his original picture book The Cave into an animated feature that tells the story through the eyes of two young boys. Set against the backdrop of the relentless bombing of Chongqing by Japanese forces during the War of Resistance against Japanese Aggression, the film aims to help younger generations connect with the city's painful past and resilient spirit.

On June 5, 1941, Japanese warplanes launched a five-hour saturation bombing raid over Chongqing, then China's wartime capital. Tens of thousands of terrified civilians rushed into public air-raid tunnels near Jiaochangkou, Shibati, and Shihuishi. Overcrowding, poor ventilation, and prolonged sealing of the tunnel entrances led to mass suffocation and trampling, killing more than 2,500 people in what became known as the "June 5 Tunnel Massacre" — the single deadliest incident in the Chongqing Bombing campaign.

Rather than adopting a conventional documentary style, The Cave takes a magical realism approach. Two orphaned boys, Haoyu and Zhuangyun, flee into an air-raid shelter during an attack but stumble into a fantastical "other world." There, they embark on a quest to find the lost elements of a "Tree of Life" — love, strength, honesty, and faith. Through trials and challenges, the boys grow braver and stronger, mirroring the indomitable spirit of the people of Chongqing during years of bombardment.

Chongqing local picture book author Liu Heyue explains his creative vision. (Photo/Liu Heyue)

"I wanted to show that even in the darkest times, ordinary people found courage and hope," Liu said. "The journey of these two characters reflects the resilience of our ancestors — they never gave up, no matter how hard the bombing got." To create the picture book and subsequent animation, Liu spent two years conducting extensive research, visiting archives, libraries, and museums to collect historical photographs, survivor accounts, and maps. The film is narrated by well-known local TV host Li Zhongji, while Liu and his family voiced many of the supporting characters — all in authentic Chongqing dialect. The familiar local accent adds a layer of intimacy and authenticity, making the historical narrative more accessible to modern audiences.

The animation also incorporates iconic Chongqing landmarks such as the People's Liberation Monument, Mountain City Alley, the banyan tree (huangge shu), the Yangtze River Cableway, and Hongya Cave, grounding the fantasy story in the city's real geography and cultural identity.

The 11-minute animated short film "The Cave", set against the historical backdrop of the Chongqing Bombing. (Photo/Liu Heyue)

Unlike grand war epics, The Cave focuses on the fates of ordinary people. Through a single bomb shelter and a group of children, the film conveys the spiritual strength of Chongqing residents in the face of suffering. It avoids melodrama, instead using a gentle, restrained tone to bring history out of textbooks and archives and into the hearts of contemporary viewers — especially the young. "Eighty-five years have passed, and the smoke of war has long cleared, but history must not be forgotten," Liu said. "I hope The Cavecan serve as a bridge between the past and the present, reminding people to remember history, cherish peace, and carry forward the unyielding spirit of Chongqing."

The short film has already been screened at local schools and community centers, receiving emotional feedback. Liu plans to release it online later this month to reach a broader audience. Each year on June 5, air-raid sirens sound across Chongqing to commemorate the victims. This year's 85th anniversary will include memorial ceremonies at the former tunnel site, where citizens lay flowers and light candles in remembrance.