NEW YORK: An award-winning documentary about the massacre carried out by Japanese soldiers in the Chinese city of Nanjing is so vivid that it left many members of the audience sobbing uncontrollably when it was shown at a film festival in New York on Thursday.

The screening of the film, entitled Nanking (the old spelling of the city's name), at the Tribeca Film Festival coincides with the 70th anniversary of the invasion.

While some members of the audience shed tears silently in the theater, others sobbed out loud.

Speaking after the film, one member of the audience said: "It is really depressing to watch that chapter of history. Now I think I can partially understand why Chinese American author Iris Chang took her own life after finishing her book The Rape of Nanking."

Nanking tells the story of the Japanese invasion of the present capital city of East China's Jiangsu Province, in the early days of World War II. At that time, Nanking was the capital of China and as part of a campaign to conquer all of China the Japanese subjected it to months of aerial bombardment. When the city fell, the Japanese army engaged in murder and rape on a horrific scale.

In the midst of the rampage, a small group of Westerners banded together to establish a safety zone where more than 200,000 Chinese found refuge. Unarmed, these missionaries, university professors, doctors, and businessmen including a German member of the Nazi party bore witness to the events, while risking their own lives to protect civilians from the slaughter.

The story is told through deeply moving interviews with Chinese survivors, chilling archival footage and photos of the events, and the testimonies of former Japanese soldiers.

The events became familiar to the film's producer, Ted Leonsis, who is also vice-chairman of AOL, in early 2005 when he stumbled across Iris Chang's obituary. It inspired him to read her book, which shocked him so much that he decided the story had to be told on screen.

Original sources

In the summer of 2005, Leonsis hired the Academy-Award-winning writer/ director team of Bill Guttentag and Dan Sturman to lead his project.

To find the materials that would bring the story of Nanking to life, Guttentag, Sturman and their production team collected thousands of pages of letters, journals and diaries for three months by trawling original sources and archives in the United States, Europe and Asia.

In December 2005, co-producer Violet Du Feng traveled to Nanjing to meet more than 30 survivors. When Leonsis, Guttentag and Sturman, and the rest of the production team arrived in China, they spent three weeks interviewing 22 survivors in the cities of Nanjing, Suzhou and Shanghai.

Filming in Japan was more difficult because the subject of Nanking is highly controversial. Those who participated in the film were found through members of the Japanese peace movement.

On returning from Asia, the production team began the final piece of filming the staged reading with actors. Filming took place in Los Angeles last August.

Their efforts were not in vain. In January, the documentary debuted at the Sundance Film Festival where it received the Editing Award. In April, it won the Humanitarian Award for Best Documentary at the Hong Kong International Film Festival.

To this day, some ultra-conservatives in Japan continue to deny or minimize the scale of the Nanking Massacre and pay annual pilgrimages to the Yasukuni Shrine where 14 Japanese class A war criminals are enshrined.

In the run-up to December, the 70th anniversary of the invasion of Nanking, the Chinese and Japanese governments have convened a joint committee of historians in an attempt to agree on a common version of the history of the Sino-Japanese conflict, including what happened in Nanking.

"It is time to repent. Denial will only lead to more mistakes," said another member of the audience.