In 1995, Iris Chang, a US historian and journalist, decided to write a book about the Nanjing Massacre, in which at least 300,000 Chinese civilians and unarmed soldiers were killed by invading Japanese troops during a six-week period starting in December 1937. To better understand the massacre, she turned to Shao Ziping in New York.

Shao, born in Nanjing in 1936, is the son of a Nationalist government diplomat to Yokohama and is the founder of the Chinese Alliance for Memorial and Justice and the Alliance in Memories of Victims of the Nanking Massacre. He has worked for decades to raise awareness of the slaughter, which took place when the city was known as Nanking.

"I told Iris about the diaries of German businessman John Rabe and that I was looking for manuscripts that might contain a lot of historical material about the massacre. I asked her to join me. But I thought that because I can speak German, I was much more likely to find the diaries before her," Shao recalled.

"But Iris was an investigative reporter, good at looking for things. She sent 100 e-mails to different people and got two or three replies. One of them was from Rabe's granddaughter, Ursula Reinhardt, who had the diaries."

In 1996, a media briefing was held in New York to publicize the discovery. Seven months later, the 2,100-plus pages that Rabe wrote from 1937 to early 1938 were translated into Chinese and published in China.

According to Shao, Chang delayed the publication of her book, The Rape of Nanking, for three months because she needed to add material culled from the diaries.

Besides Rabe's diaries, which are held at the library of Yale University, Chang also found the diaries of Minnie Vautrin, a US missionary and teacher in Nanjing, which also contain precious material about the massacre.

Rabe's and Vautrin's diaries are now among the most important source materials about the event. Along with other material recorded by Nanjing-based expats who chose to stay in the city, the diaries not only confirm the atrocities committed by Japanese soldiers and officials from a third-party perspective, but also reveal a humanitarian history about the authors' selfless help to the Chinese people.

Japanese troops captured Nanjing, which was the capital of China at the time, on Dec 13, 1937. Within three weeks, unsupervised soldiers and military officials had turned on the city and killed huge numbers of unarmed civilians and soldiers in a variety of brutal ways - including being buried or burned alive, decapitation, bayoneting, and shooting.