Some of the most chilling images in the film were captured by John Magee, an Episcopal who chose to stay in occupied Nanjing and set up a make-shift hospital to take care of wounded soldiers and refugees. He filmed the atrocities on a 16mm camera and had risked his life to preserve the films.

Controversy

Despite its emphasis on primary sources, the documentary still stirred up controversies over the interpretations of the massacre. On January 24, two days before the film's premiere at the Sundance Film Festival, Japanese filmmaker Satoru Minzushima, who also runs a Japanese satellite-television station, lashed out at Nanking saying it was based on an "erroneous understanding of history," and announced that he would produce his own film, provisionally entitled The Truth about Nanking, to rebut it.

On June 19, about 100 Japanese governing party lawmakers denounced the Nanjing Massacre as a fabrication, saying that there was no evidence to prove there were mass killings by Japanese soldiers in the city. Nariaki Nakayama, head of the group created to study World War II historical issues and education, said documents from the Japanese government's archives indicated that about 20,000 people were killed. However, according to the post-World War II International Military Tribunal for the Far East, "estimates indicate that the total number of civilians and prisoners of war murdered in Nanjing and its vicinity during the first six weeks of the Japanese occupation was over 200,000. Approximately 20,000 cases of rape occurred in the city during the first month of the occupation."

"My personal conviction is that the incident really happened. The discussion around whether it is 300,000 people who were killed, 200,000 people, or 100,000 people doesn't matter. Trying to boil down this part of history to numbers is not a healthy exercise," said Leonsis, the day after the movie's premiere in Beijing. He said he was really touched by the kindness of the Western people who stayed behind to save lives and hoped that moviegoers would reflect on what their choices would be in a similar situation.

Leonsis said his team had cooperated well with Chinese partners. The State Administration of Radio, Film and Television approved the screening of the film in China in 48 hours and the film's Chinese distributor Huaxia Films worked fast to squeeze the theatrical release of Nanking between Pirates of the Caribbean At World's End and Transformers, making China the first nation to see the movie released in theaters. Up to early July, the movie had sold its contribution rights to about 10 countries, but Japan is not on the list. "We want the movie to be seen by as many people as possible," said co-director Dan Sturman.

Leonsis emphasized the film had received zero interference, zero influence and zero editing from the Chinese Government. "I think it is very wise. That a third-party without any agenda, did the research, did the movie and paid for it has made the movie credible," he said.