They were mostly children when Japanese invaders captured Nanjing, then China's capital, on Dec. 13, 1937 and started six weeks of mass killings, rape and pillage that resulted in the deaths of about 300,000 Chinese.

Eighty years later, survivors of the Nanjing Massacre are in their twilight years and number less than 100. Chinese historians are racing against time to document their recollections, before the stories fade into oblivion with their passing.

"A sense of urgency keeps stinging me," said Zhang Jianjun, curator of the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders.

In September last year, he launched an oral history project in collaboration with local historians to document the accounts of the last group of survivors.

"We were saddened by the news as one survivor after another passed away," said Gao Xudong, a junior at Nanjing University who participated in the project. "They are part of the city's history and we have the obligation to keep their memories alive."

This month, two books were published: one collecting testimonies of 49 survivors to the atrocities and the other detailing their lives thereafter. They were based on transcripts of the survivors' accounts, totally 1.2 million words, documented by more than 50 participants who spent nearly six months conducting more than 150 interviews.

In addition to blow-by-blow accounts of the massacre, the books also detail how the survivors painstakingly tried to heal their wounds, and how they managed to lead a normal life over the past 80 years, offering a wider and more personal perspective to one of the most barbaric episodes of World War II.

Zhang Sheng, a history professor with Nanjing University and a collaborator in the project, said the books marked new efforts by Chinese historians on the research of the infamous massacre. In the past, they had placed more emphasis on countering the denials of the massacre made by some Japanese right-wing politicians.

"History is more than some cold statistics in books," said Zhang Sheng. "It is also about lives of individuals in times of turmoil and disaster."

"Every time we heard a survivor recount his or her story, we experienced again the trauma and fear the war has inflicted on the individual," he said.

The participants, who are mostly university students, said revisiting the massacre 80 years ago gave them new perspectives on issues such as life and death, war and peace.

"Interviewing the survivors prompted us to ask questions we had never asked before," said Zhang Yisi, one of the participants. "Now we have a deeper understanding of how our country has come a long way from such a low point in history to prosperity."

A similar project is underway. Zhu Chengshan, a former curator of the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders, has started to research how the massacre has affected the extended families of the survivors in the long term.

On Wednesday, when China marks the fourth National Memorial Day for Nanjing Massacre Victims, a new section of the memorial hall featuring accounts of witnesses and survivors will also be open to the public.

"This research focuses on how historical events impact the lives of individuals and their families, which allows people to empathize more with the trauma of the victims," said Zhang Jianjun, the curator of the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders.