"When they came in they killed my father. My mother was holding a child. They grabbed and smashed the baby to death. They ripped off my mother's clothing...". The stories of survivors torment a young Iris Chang: images of a a bloody massacre and a river running red...But when Iris wanted to find out more, she found nothing written on the massacre in English. "Why had it disappeared from the history books?"

Iris's grandparents fled Nanking when the streets began to fill with blood. After she saw a picture of a man who'd been decapitated, she knew this was a story she had to tell: "In a single moment I saw the fragility of human life." She began interviewing survivors.

As the testimonies emerged, the full scale of the atrocities came to light. One British reporter compared the invading Japanese to Attila and the huns. Even the Japanese reporters could not believe the brutality of their soldiers: "I saw a mass killing..blood splattered everywhere. The chilling atmosphere made one's hair stand on end and limbs tremble with fear."

Yet amid the horror, a story of heroism came to light. John Rabe, a German businessman, headed a committee of foreigners who stayed behind in Nanking to create a Safety Zone. They saved thousands from the slaughter. Rabe alone sheltered 600 refugees in his own home. Ironically, Rabe was a member of the Nazi party: an influence he used to dissuade the Japanese from their rampage.

For Iris, the more she learned of the massacre, the more she learned of "the potential of all human being for evil, not just the Japanese, not just the Germans". Yet for million, her courageous story to bring this forgotten tragedy to live, is one of the century's most inspiring.