Sirens blared and thousands of doves were released as Chinese President Xi Jinping presided over a sombre ceremony in Nanjing marking 80 years since the wartime massacre in the city by Japanese troops.

Several thousand black-clad soldiers, civil servants and students with white flowers pinned to their jackets braved chilly temperatures at a monument to a dark World War Two chapter that still divides the two countries.

An elderly man looks on as he attends a memorial ceremony at the Nanjing Massacre Memorial Hall on the second annual national day of remembrance to commemorate the 80th anniversary of the massacre in Nanjing on December 13, 2017. Photo: AFP/Chandan Khanna.

But while vowing never to forget the “great catastrophe” wrought by “Japanese militarism” in a speech to the mourners, a top Chinese official also stressed the need for the two rivals to move forward.

“China and Japan are close neighbours, neighbours who can’t move away,” said Yu Zhengsheng, a former member of China’s top Communist leadership who now chairs a parliamentary body.

China and Japan should build on their “long, rich history” of links to deepen “friendship”, Yu said, avoiding reference to bitter disputes over the massacre.

According to China, 300,000 civilians and soldiers were killed in a frenzy of murder, torture, rape, arson and looting in the six weeks after invading Japanese troops seized Nanjing, then the capital city, on December 13, 1937.

It remains a source of bad blood due to disagreement over the extent of the slaughter and periodic denials by Japanese arch-conservatives that it even took place.

Officially, Japan concedes that “the killing of a large number of noncombatants, looting and other acts occurred” but says it is “difficult” to determine precise figures.

The issue receded during the Cold War but has re-emerged in recent decades, with China now striking an increasingly muscular stance under Xi, while critics say Japanese revisionists have grown bolder under conservative leader Shinzo Abe.

“There are current conflicts between the two countries, so historical issues are re-emerging. All history is contemporary,” Liang said.

But fewer than 100 people designated as massacre “survivors” remain alive, and both sides have repeatedly expressed desire to look ahead and avoid rocking their huge trade relationship.

“Xi cannot avoid anti-Japanese movements, as nationalism is a source of his political power. But deep down he must be hoping to improve ties with Japan,” said Mitsuyuki Kagami, professor of China studies at Aichi University.

Soldiers carried eight large wreaths representing the decades into the memorial site as sorrowful music played.

A “peace bell” was then rung. Sirens blared across the city for one minute and car horns could be heard as well.

‘Deep remorse’

The two countries have struggled to put Japan’s wartime aggression behind them and Abe, the grandson of a wartime minister, has been accused of trying to gloss over history.

In 2015, he expressed “deep remorse” for Japan’s actions in Asia, but also said future Japanese generations need not continually apologise, drawing criticism in China and South Korea, another wartime victim.

Japanese politicians have also repeatedly angered Asian neighbours by visiting Tokyo’s Yasukuni Shrine commemorating Japan’s military dead, including convicted war criminals.

China’s Nanjing toll is disputed even by some western academics who put it as low as tens of thousands, but no respected historians dispute that a massacre occurred.

China suffered immense loss of life at Japan’s hands, reserving special anger over a sense that Tokyo, unlike Germany, has never fully atoned for the war.

Relations plunged in 2005 as China was swept by rare anti-Japan protests denouncing its war conduct.

But analysts say China’s stability-obsessed leaders are deeply fearful of letting such passions burst out again as it could pose a potential political quandary for the ruling Communist Party.

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