Zhang Yimou, one of China's best-known directors, is banking on heartthrob Christian Bale to help boost the country's chances of winning an Oscar, with his latest film on a tragic chapter in the nation's history.

"The Flowers of War", China's Academy Award entry for best foreign language film, centres around a mortician (Bale) who gets caught up in the 1937 Nanjing Massacre and has to save a group of school girls from the clutches of the Japanese.

On the way he becomes involved with a high-class Chinese courtesan, finding both love and personal redemption.

The film, which hits Chinese screens on Friday followed a week later by a limited release in the United States, holds little back in its graphic depiction of the events of more than eight decades ago, a story everyone in China knows well.

"It's far more a movie about human beings and the nature of human beings' responses to crisis, and how that can reduce people to the most animalistic behaviour but also raise them up to the most honourable behaviour you could ever witness," said Bale.

China says invading Japanese troops slaughtered 300,000 men, women and children in Nanjing, then known as Nanking. An Allied tribunal after World War II put the death toll at about 142,000.

But some Japanese historians say the massacre has been exaggerated and some conservatives deny there was even a massacre.

Sino-Japanese ties have been overshadowed for years by what Beijing says has been Tokyo's refusal to admit to atrocities committed by Japanese soldiers in the country between 1931 and 1945.

"Obviously there are fewer people in the West who are familiar with the Rape of Nanking. Myself, I knew about it. I owned the book and had never read it. So I came to know far more about it," Bale added.

Billed as the first Chinese movie to star a major Western actor, the country has high hopes it will snag an Oscar.

Zhang downplayed that.

"We can work as hard as possible but really it's up to the gods. I really don't understand what the rules are for getting an Oscar," he said.

"The Flowers of War", China's Academy Award entry for best foreign language film.