This information has come from Iris Chang's book The Rape of Nanking: The Forgotten Holocaust of World War II, Basic Books, 1997.
On December 13, 1937, Nanking, the capital city of Nationalist China,fell to the Japanese. For Japan, this ws to have been the decisive turning point in the war, the triumphant culmination [ending] of a half-year struggle against Chiang Kai-shek's armies in the Yangtze Valley. ...
We now [1997] think of Nanking as a turning point of a different sort. What happened within the walls of that old ity stiffened Chinese determination to recover it and ti expel [get rid of] the invader. The Chinese government retreated, regrouped, and ultimately outlasted Japan in a war that ended only in 1945. In those eight years Japan would occupy Nanking and set up a government of Chinese collaborators; but it would never rule with confidence or [in Iris Chang's point of view] legitimacy, and it could never force China's surrender. to the larger world, the "rape" of Nanking - as it was immediately called - turned public opinion against Japan in a way that little else could have. [this point has limitations as Japan was still able to have some diplomatic relations]

That is still the case in China, where several generations have been taught of Japan's crimes and of its failure to this day [1997] to atone for them. Sixty years later, the ghosts of Nanking still haunt Chinese-Japanese relations.

...The Japanese sack of China's capital was a horrific event. The mass execution of soldiers and the slaughtering and raping of tens of thousands of civilians took place in contravention [against]of all rules of warfare. What is still stunning is that it was public rampage, evidently to terrorize. It was carried out in full view of international observers ... And it was not a temporary lapse of military discipline, for it lasted seven weeks. this is the terrible story that iris Chang tells so powerfully in this first, full study in English of Nanking's tragedy.

We may never know precisely what motivated Japanese commanders and troops to such bestial behaviour. But Ms Chang shows more clearly than any previous account just what they did. in doing so she employs a wide range of source materials, including the unimpeachable testimony of third-party observers: the foreign missionaries and businessmen who stayed in the defenseless city as the Japanese entered it. One such source that Ms Chang has uncovered is the diary - really a small archive - of John Rabe, the German businessman and National Socialist [NAZI] who led an international effort to shelter Nanking's population. Through Rabe's eyes we see the dread and courage of Nanjing's inhabitants as they confront, defenseless, the Japanese onslaught. Through Ms Chang's account we appreciate the bravery of RAbe and others who tried to make a difference as the city was being burned and its inhabitants assaulted; as hospitals were closed and morgues filled; and as chaos reigned around them.

We read too of those Japanese who understood what was happening, and felt shame.

...Americans think of World War Ii as beginning on December 7, 1941, when Japanese carrier-based airplanes attacked Pearl Harbor. Europeans date if from September 1, 1939, and the blitzkrieg assault on Poland by Hitler's Luftwaffe and Panzer divisions. Africans see an even earlier beginning, the invasion of Ethiopia by Mussolini in 1935. Yet Asians must trace the war's beginnings all the way back to Japan's first steps towards the military domination of East Asia - the occupation of Manchuria in 1931.

Just as Hitler's Germany would do half a decade later, Japan used a highly developed military machine and a master-race mentality to set about establishing its right to rule its neighbours. Manchuria fell quickly to the Japanese, who established their government of Manchukuo,, ostensibly under their puppet, the deposed emperor of China, but in fact run by the Japanese military. Four years later, in 1935, parts of Chahar and Hopeh were occupied; in 1937 Peking, Tientsin, Shanghai, and finally Nanking fell. ...

...we do know the story of Nanking because some foreigners witnessed the horror and sent word to the outside world at the time, and some Chinese survived as eyewitnesses. If one event can be held up as an example of the unmitigated evil lying just below the surface of unbridled military adventurism, that moment is the Rape of Nanking.

...The broad details of the Rape are, except among the Japanese, not in dispute. In November 1937, after their successful invasion of Shanghai, the Japanese launched a massive attack on the newly established capital of the Republic of China. When the city fell on December 13, 1937, Japanese soldiers began an orgy of cruelty seldom if ever matched in world history. Tens of thousands of young men were rounded up and herded to the outer areas of the city, where they were mowed down by machine guns, used for bayonet practice, or soaked with gasoline and burned alive. For months the streets of the city were heaped with corpses and reeked with the stench of rotting human flesh. Years later experts at the International Military Tribunal of the Far East (IMTFE) estimated that more than 260,000 noncombatants died at the hands of Japanese soldiers at Nanking in late 1937 and early 1938, though some experts have placed the figure at well over 350,000.
...for its aim (This book) is not to establish a quantitative record to qualify the event as one of the great evil deeds of history, but to understand the event so that lessons can be learned and warnings sounded. ...

...It is certainly true that in the 20th century, when the tools of mass murder were fully refined, Hitler killed about 6 million Jews, and Stalin more than 40 million Russians, but these deaths were brought about over some few years. In the Rape of Nanking the killing was concentrated within a few weeks.

...the Rape of Nanking represents one of the worst instances of mass extermination. ...The death toll of Nanking-one Chinese city alone-exceeds the number of civilian casualties of some European countries for the entire [Second World] war. Great Britain lost a total of 61,000 civilians, France lost 108,000, Belgium 101,000, and the Netherlands 242,000. ...Indeed, whether we use the most conservative number - 260,000 - or the highest - 350,000 - it is shocking to contemplate that the deaths at Nanking far exceeded the deaths from the American raid on Tokyo (an estimated 80,000-120,000 deaths) and even the combined death toll of the two atomic blasts at Hiroshima and Nagasaki by the end of 1945 (estimated at 140,000 and 70,000 respectively).

The Rape of Nanking should be remembered not only for the number of people slaughtered but for the cruel manner in which many met their deaths. Chinese men were used for bayonet practice and in decapitation contests. An estimated 20,000-80,000 Chinese women were raped. Many soldiers went beyond rape to disembowel women, slice off their breasts, nail them alive to walls. Fathers were forced to rape daughters, and sons their mothers, as other family members watched. Not only did live burials, castration, the carving of organs, and the roasting of people become routine, but more diabolical tortures were practiced, such as hanging people by their tongues on iron hooks or burying people to their waists and watching them get torn apart by German Shepherds. So sickening was the spectacle that even the Nazis in the city were horrified, one proclaiming the massacre to be the work of "bestial machinery."

Yet the Rape of Nanking remains an obscure incident. Unlike the atomic explosions in Japan or the Jewish Holocaust in Europe, the horrors of the massacre at Nanking remain virtually unknown to people outside Asia. ...Only in Robert Leckie's Delivered from Evil: The Saga of World War II (1987) did I find a single paragraph about the massacre: "Nothing the Nazis under Hitler would do to disgrace their own victories could rival the atrocities of Japanese soldiers under Gen. Iwane Matsui."

I first learned about the Rape of Nanking when I was a little girl. The stories came from my parents, who had survived years of war and revolution ...They had grown up in China in the midst of World War II and after the war fled with their families, first to Taiwan and finally to the United States to study at Harvard and pursue academic careers in science. ...But they never forgot the horrors of the Sino-Japanese War, not did they want me to forget. They particularly did not want me to forget the Rape of Nanking. Neither of my parents witnessed it, but as young children they had heard the stories, and these were passed down to me. The Japanese. I learned, sliced babies not just in half but in thirds and fourths, they said; the Yangtze River ran red with blood for days. Their voices quivering with outrage, my parents characterised the Great Nanking Massacre, or Nanjing Datusha, as the single most diabolical incident committed by the Japanese in a war that killed more than 10 million Chinese people.

Throughout my childhood Nanjing Datusha remained buried in the back of my mind as a metaphor for unspeakable evil. But the event lacked human details and human dimensions. It was also difficult to find the line between myth and history. ....If the Rape of Nanking was truly so gory, ...then why hadn't someone written a book about it?

...Nancy Tong, and independent filmmaker who had produced and co-direted with Christine Choy In the name of the Emperor. Shao Tzuping and Nancy Tong helped plug me into a network of activists, many of them first-generation Chinese Americans and Chinese Canadians who, like me, felt the need to bear witness [talk about] the event, to document and publicise it,and even to seek restitution for the atrocities of Nanking before all the surviving victims passed away.

Others wanted to pass their wartime memories down to their children and grandchildren, fearful that their assimilation into North American culture might cause them to forget this important part of their historical heritage.

The Tiananmen Square massacre of 1989. [how knowledge of this event came to be talked about again]
What strengthened much of this newly emerging activism was the Tiananmen Square massacre of 1989 which prodded Chinese communities all over the world to form networks to protest actions of the People's Republic of China. The pro-democracy movement left behind vast, intricate webs of Internet relationships; out of this network a grassroots movement emerged to promote the truth about Nanking.

In urban centres with high concentrations of Chinese - such as the San Francisco Bay Area, New York City, Los Angeles, Toronto and Vancouver - Chinese activists organised conferences and education campaigns about Japanese crimes during World War II. They exhibited films, videos, and photographs of the Nanking massacre in museums and schools, posted facts and photographs on the Internet, and even placed full-page advertisements on the subject in newspapers like the New York times.

...That the Nanking massacre of my childhood memories was not merely folk myth but accurate oral history hit me in December 1994, when I attended a conference sponsored by the Global Alliance for Preserving the History of World War II in Asia...

...nothing prepared me for these pictures - stark black and white images of decapitated heads, bellies ripped open, and nude women forced by their rapists into various pornographic poses, their faces contorted into unforgettable expressions of agony and shame.

...The pictures up on that wall in Cupertino illustrated that ...hundreds of thousands could have their lives extinguished, die at the whim of others, and the next day their deaths would be meaningless. But even more telling was that those who had brought about these deaths ...could also degrade the victims and force them to expire in maximum pain and humiliation. I was suddenly in a panic that this terrifying disrespect for death and dying, this reversion in human and social evolution, would be reduced to a footnote of history, treated like a harmless glitch in a computer program ..., unless someone forced the world to remember it.

[Why hadn't it been written about?]
...the Rape of Nanking did not penetrate the world consciousness in the same manner as the Holocaust or Hiroshima because the victims themselves had remained silent.
...I now wondered why the victims of this crime had not screamed out for justice. ...It became clear to me that the custodian [keeper] of the curtain of silence was politics. The People's Republic of China, the Republic of China, and even the United States had all contributed to the historical neglect of this event for reasons deeply rooted in the [influence of] the cold war [communist countries versus democratic or capitalist or western countries].

After the 1949 Communist revolution in China, neither the People's republic of China nor the Republic of China demanded wartime reparations [payment for damages] from Japan as Israel had from Germany because the two governments were competing for Japanese trade and political recognition. And even the United States, faced with the threat of communism in the Soviet Union and mainland China, sought to ensure the friendship and loyalty of its former enemy, Japan. In this manner, cold war tensions permitted Japan to escape much of the intense critical examination that its wartime ally [Nazi Gemany] was forced to undergo.

[Another reason why it wasn't talked about] atmosphere of intimidation in Japan stifled open and scholarly[educated] discussion of the Rape of Nanking, further suppressing knowledge of the event.

In Japan, to express one's true opinions about the Sino-Japanese War could be, and even life-threatening. (In 1990 a gunman shot Motoshima Hitoshi, mayor of Nagasaki, in the chest for saying that Emperor Hirohito bore some responsibility for World War II). This pervasive sense of danger has discouraged many serious scholars from visiting Japanese archives to conduct their research on the subject ... I was told in Nanking that the People's Republic of China rarely permits its scholars to journey to Japan for fear of jeopardising their physical safety. Under such circumstances, gaining access to Japanese archival source materials about the Rape of Nanking has been exceedingly difficult for people outside of the island nation [of Japan]. [remember that Iris Chang is speaking from 1997 here so this situation has more than likely changed].

...What baffled and saddened me during the writing of this book [in 1997] was the persistent Japanese refusal to come to terms with its own past. It is not just that Japan has doled out less than 1 percent of the amount Germany has paid in war reparations to its victims....many Japanese war criminals continued to occupy powerful positions in industry and government after the war. ...the Japanese have enshrined their war criminals in Tokyo.

...Strongly motivating me throughout this long and difficult labour was the stubborn refusal of many prominent Japanese politicians, academics, and industrial leaders to admit, despite overwhelming evidence, that the Nanking massacre had even happened.

In contrast to Germany, where it is illegal for teachers to delete the Holocaust from their history curricula, the Japanese have for decades systematically purged [got rid of] references to the Nanking massacre from their textbooks. They have removed photographs of the Nanking massacre from museums, tampered with original source material...Even respected history professors in Japan have joined right-wing forces to do what they perceive to be their national duty: discredit reports of a Nanking with these words: "Even if twenty or thirty people had been killed, it would have been a great shock to Japan. Until that time, the Japanese troops had been exemplary [good in their behaviour] It is [was] this deliberate attempt by certain Japanese to distort history that most strongly confirmed in me the need for this book.

...Germany is today a better place because Jews have not allowed that country to forget what it did during World War II.

...This book describes two related but discrete atrocities. One is the Rape of Nanking itself, the story of how the Japanese wiped out hundreds of thousands of innocent civilians ...another is the cover-up, the story of how the Japanese, emboldened by the silence of the Chinese and Americans, tried to erase the entire massacre from public consciousness, thereby depriving its victims ...

...The ugliest aspects of Japanese military behaviour during the Sino-Japanese War have indeed been left out of the education of Japanese schoolchldren. But they [Japanese governments] have also camouflaged the nation's role in initiating the war within the carefully cultivated myth that the Japanese were the victims, not the instigators, of World War II. The horror visited on the Japanese people during the atomic bombings of Hiroshima and Nagasaki helped this myth replace history.

...the Japanese managed to avoid the moral judgement of the civilised world that the Germans were made to accept for their actions in this nightmare time.

...As the Nobel laureate Elie Wiesel warned years ago, to forget a holocaust is to kill twice.