When Sun Chuan Ben fixed roofs at a Japanese base in the waning days of World War II, he was told not to ask questions. But he wondered why so many buildings were stacked with cages of yellow rats.
Only later did he, and other Chinese, begin to learn what went on at Unit 731, a huge complex in northeast China. As both Chinese and surviving Japanese soldiers now allege, most recently in testimony before a Tokyo court, between 1938 and 1945 the germ-warfare research unit conducted experiments on Chinese people and worked on methods to spread disease, using animals from rats to camels. Japan has never officially acknowledged any wrongdoing at Unit 731.
That is one reason why, when Japanese Prime Minister Junichiro Koizumi paid homage to Japan's war dead at a shrine last week, and when Japan's Education Ministry this summer approved history textbooks that whitewash or deny mass crimes by Japanese troops in Korea and China - those acts echo loudly in Asia in a way that is unpredictable, largely negative, and easily exploitable by right-wing factions.
"I am not against the Japanese people, I do not hate them," says Mr. Sun. "But I will not be friends with those Japanese who wish to deny what happened."
Such vocal disagreements also symbolize why, while Japan is China's top trading partner - ahead of the US - the China-Japan relationship remains the thickest and most complex Gordian Knot in Pacific relations.
These latest echoes also illustrate the complex psychological legacy of the war in Asia - something never reconciled in this part of the world, or examined in the way that Nazi crimes in Europe have been over time. Experts say it's a main reason why the security and diplomatic relationships that took hold in Europe after World War II have not taken place in this part of the world.
"As the 21st century begins, Asia's security environment seems likely to be shaped by the distrust, if not rivalry, between China and Japan that is the legacy of the past century," says Richard Solomon, director of the US Institute of Peace in Washington and a former China specialist at the US State Department.
The Unit 731 museum - which opened in June with 12 rooms of exhibits of rusty equipment, gas masks, photo documentaries, and acres of preserved ruins - is just one of many highly produced permanent exhibitions built in China during the 1990's, under an official campaign to highlight and educate about "the Anti-Japanese War of Aggression," the term given to Japan's 13-year occupation of China.
"When we see Koizumi walk to the shrine, we want to invite him to come here," says Wang Peng, manager of the exhibit. "The Japanese deny this germ-warfare center ever existed."
Koizumi, in his statement at the Yasukuni shrine last week, offered "profound remorse ... to all the victims of the war" and said due to a "mistaken policy ... Japan imposed ... immeasurable ravages and suffering ... to the people of ... Asia."
Precise knowledge about Unit 731 is sketchy by Western standards. The Japanese blew up the laboratories before they left, and China spent four more years in a civil war that brought in Communist rule. Most of the substantial evidence about the complex has come from former Japanese workers who broke their silence late in life.
One such worker, Yoshio Shinozuka, testified last year that he cultivated fleas that were exposed to rats with bubonic plague. Other accounts compiled in recent years suggest that Chinese prisoners were subjected to bubonic plague, frostbite, extreme heat, toxic gas, amputation, vivisection, and electric shocks. Some 3,000 people are estimated to have died inside the complex - though Chinese officials say the number is higher.
More deeply in the Chinese mind, say some local scholars, is a sense that by never fully apologizing, and by minimizing wartime atrocities, the Japanese are subtly jabbing at the Chinese - implying cultural superiority by suggesting that it was not China, but the United States, that defeated Japan in 1945. "It is a way for Japanese to tell us we are inferior," says one retired scholar.
Japanese sources say Tokyo has apologized on three separate occasions, and that the Chinese are continuing to use the war as a "history card" to gain leverage and sympathy internationally. "The Chinese keep banging us, beating us. What do they want? They teach young people that Japanese are untrustworthy, and beasts," says one well-placed Japanese official. "We don't teach our children they are beasts."
Some China scholars say the Chinese Communist Party also uses the war as a way to legitimize itself through a patriotic appeal. Some point out that while Beijing has sought to highlight Japanese aggression in World War II, it is woefully lacking in coming to terms with its own history - events like the Great Famine of the late 1950s, in which millions died, the Cultural Revolution, and the more recent Tiananmen Square episode of 1989.
One diplomat speculates that the war is kept alive in China partly because the Chinese Communists were never were able to confront the Japanese military directly after the war. The government-in-exile of Chiang Kai Shek represented China at the 1951 San Francisco Peace Treaty.
In 1972, the Japanese sought quickly to establish relations with China after US President Nixon cleared the way, which led to a rapproachment without much historical reconciliation. Under a 1978 peace treaty, China gave up its right to claim reparations from the Japanese government, in the view of some experts. "In the heart of the Communist army, there was never a chance to say 'We won,' " says the diplomat. "They have not lost that obsession."
Yet Chinese say the main reason the war is kept alive is due to what they regard as Japan's two decade-long campaign to deny wartime atrocities. Cases such as Unit 731 pale in comparison with the Japanese massacre at Nanjing between December 1937 and May, 1938 - when an estimated 300,000 Chinese died. Japanese textbooks never treated the Nanjing event in anything but a cursory manner, and Tokyo has never taken responsibility.
"Not until 1994 were Japanese schoolchildren taught that [Emperor] Hirohito's army was responsible for the deaths of at least 20 million Allied soldiers and Asian civilians during World War II," writes author Iris Chang in "The Rape of Nanjing," a 1996 account of Japanese brutality and the contemporary effort by Tokyo to sanitize its past.
"When the Japanese came out with a textbook that denied the Nanjing massacre and lied about the Japanese invasion, when they started to build monuments to their troops, that hurt us - and we realized it was time to do something," says Han Xiao, an official with the Unit 731 exhibit. "We want these museums to tell the truth to all peoples of the world, and especially to educate the younger generations, so it won't happen again."
Some Chinese students interviewed felt that "we should not forget," as one put it. But many also look to Tokyo for the latest music and fashions. At an exhibition of Japanese student art at a gallery in Harbin, another student says: "Let the past be the past. I think it was natural for Kouizumi to visit the shrine."