This month 75 years ago, the people of Nanking, China’s ancient capital city, were in the midst of one of the worst atrocities in history, the infamous Rape of Nanking.

The truth of what actually happened is at the center of a bitter dispute between China and Japan that continues to play out in current relations.

Many Chinese see Japan’s election last month of ultraconservative nationalist Shinzo Abe as prime minister as just the latest in a string of insults. And it was recently reported that Japan is considering rolling back its 1993 apology regarding “comfort women,” the thousands of women the Japanese army sexually enslaved during World War II.

In 1937, the Japanese Imperial Army, captured Nanking on Dec. 13. No one knows the exact toll the Japanese soldiers exacted on its citizens, but a postwar Allied investigation put the numbers at more than 200,000 killed and at least 20,000 women and girls raped in the six weeks after the city fell.

In 2006, we traveled to China and to Japan to interview victims and soldiers who took part in the massacre.

One former Japanese soldier explained, without a hint of regret: “We all drew straws, and the man who pulled out the one marked first, he brushed off her face tenderly and treated her pretty, yes, and then proceeded to rape her. As their daughter was being raped, the parents would come outside and gesture to us, ‘Please spare her!’ They’d bang their heads on the ground and plead with us. We’d take one girl and five of us would hold her down.”

In China, a 79-year-old man tearfully described how, at 9 years old, he watched a soldier bayonet his mother to death as she breast-fed his brother. Another man saw his 13-year-old sister sliced in half by a Japanese soldier after she resisted being raped. Elderly women told harrowing stories of the rapes they endured as young girls.

It was the mass rapes in Nanking and the brutalization of an entire populace that eventually convinced Japanese military leaders that they needed to contain the chaos. Japanese soldiers began rounding up women and forcing them to serve as sex slaves in so-called comfort stations.

This is what most historians believe. But not in Japan, where a large faction of conservatives, led by Abe, denies that the Japanese military forced women into sexual slavery. They maintain that any suggestion to the contrary is simply anti-Japanese propaganda and probably spread by China.

At the furthest end of the spectrum, the minimizing turns to flat-out denial; one professor we interviewed at a top Japanese university adamantly insisted there were no killings or rapes in Nanking.

Not surprisingly, all this minimizing and denial enrages the Chinese and others in Asia. But this is a familiar pattern.

Abe has visited the controversial Yasukuni shrine in Tokyo and has said he plans to visit again as prime minister. This is the place where the souls of more than 2 million Japanese war dead are said to be enshrined. Among them are 14 men convicted at the end of World War II of what are known as Class-A war crimes, including Iwane Matsui, the general who led Japanese forces in Nanking.

To the Chinese, every visit by an official is like ripping open an unhealed wound. Former Prime Minister Junichiro Koizumi went there six times, and his 2005 visit resulted in anti-Japanese riots in China.

It’s also informative to walk just a few yards to the Yushukan, the museum affiliated with the Yasukuni shrine. There, as we surveyed the exhibits on the Great East Asian War (World War II to much of the rest of the world), we were surprised to learn that Franklin D. Roosevelt had forced Japan to go to war in a calculated effort to lift the U.S. out of the Depression. (This exhibit was recently revised to omit the Depression reference; now it just says the U.S. forced Japan into bombing Pearl Harbor.)

Then there’s the exhibit that argues that Japan’s “entry into” other Asian countries was simply an effort to help them throw off the yoke of Western colonization. The museum claims that the Japanese leaders who were tried as war criminals were heroic. A tiny section about Nanking makes no mention of atrocities.

All this revisionism is interspersed with militaristic displays. And crucially, these are not a handful of dusty exhibits in an out-of-the-way place; the Yasukuni complex occupies 25 acres of prime Tokyo real estate.

Fueled by such an aggrieved interpretation of Japan’s wartime past, Abe and his party are leading efforts to amend Article 9 of the nation’s postwar constitution, which mandates that Japan not maintain a standing army. This comes at a time of escalating tension with China, much of it focused on the Senkaku islands.

And Abe’s government is considering revising what is known as the Kono Statement, a 1993 apology Japan made for the comfort women, an issue of great meaning to China and other nations that had women forced into sexual slavery.

It seems unlikely that the region will erupt into armed conflict over three tiny islands or repeal of the apology. And it can be argued that the move to amend the constitution shouldn’t be a cause for great alarm because Japan already has a well-armed self-defense force.

What is alarming is that the leaders of Japan — and a large and vocal minority of its citizens — have an understanding about their country’s wartime history that is grounded primarily in fiction. The Rape of Nanking is not in dispute. There is abundant eyewitness testimony from foreign observers, victims and Chinese and Japanese soldiers; contemporaneous news accounts; horrifying forensic and photographic evidence; and even film footage, surreptitiously shot by an American missionary.

Japanese denial in the face of all this ensures that a historical event will continue to fan the flames of anger and distrust. The sooner the facts are recognized and Japanese leaders renounce paying tribute to mass killers and rapists, the sooner true healing can begin.

Bill Guttentag is a lecturer at the Stanford Graduate School of Business. He and Dan Sturman directed the documentary film “Nanking,” which won a Peabody Award in 2009. They wrote this for the Los Angeles Times. It was distributed by MCT Information Services.