When the Imperial Japanese Army invaded Nanjing in 1937, hundreds of thousands of innocent civilians and prisoners of war were slaughtered, many of the women raped, in what was then the capital of China.

The horror is known as the Nanjing Massacre, or The Rape of Nanking.

While most foreigners fled the city before the Japanese invasion, 22 of them remained behind.

Some of the American missionaries who stayed not only witnessed the atrocities of the Japanese soldiers, they also risked their lives to save Chinese civilians from the brutal rampage at the hands of Japanese invaders and smuggled out important evidence of the massacre to show the rest of the world.

The American missionaries, who included educators, doctors and ministers, were all determined to do what they could to help Chinese civilians.

One missionary, Father John Magee, filmed the aftermath of the atrocities, while another, George Fitch, risked his life to clandestinely smuggle the films out of the city.

Dr Robert Wilson saved countless lives as the only remaining surgeon in Nanjing, and Minnie Vautrin, a heroic teacher, is credited with singlehandedly preventing hundreds of rapes.

Their stories come to life through letters and diaries they wrote at the time.

A docu-drama, Scars of Nanking, which is based on their stories, will premiere on the History Channel on Wednesday morning and be simulcast in China. The timing marks the 80th anniversary of the brutal massacre.

Chris Humphrey, the executive producer, said the Nanjing Massacre is one of the true tragedies in world history.

“It is mind-boggling in its cruelty. It’s hard to comprehend how the human being can stoop to such low levels of barbarity — with levels of cruelty not even seen in the animal kingdom,” he told China Daily.

Humphrey said it’s a deeply important subject to keep alive because it’s a reminder to all that events like this should never ever be repeated.

“We must learn from these sorrowful milestones in history in order to ensure it doesn’t happen again. But more simply than that, we should always remember that love wins over hate,” he said.

The docu-drama is a joint production by the A+E Networks of the US and Jiangsu Broadcasting Corp based in Nanjing, where the infamous massacre occurred.

Bu Yu, president of Jiangsu Broadcasting Corp, told China Daily that news media bear the responsibility to reveal the truth.

His team has not only done extensive research within China, but has also travelled the world to places like the US National Archives, the Hoover Institution at Stanford University, the Divinity School Library of Yale University, Harvard-Yenching Library, the National Archives of Japan and the Japan Newspaper Museum.