The 1937 massacre is known in the West as the "Rape of Nanking." Bale plays an American priest in the film "The Flowers of War."
It is an adaptation of a Chinese-language novel about 13 sex workers in Nanjing who volunteered to replace university students as escorts for invading Japanese soldiers.
The American priest leads a church that shelters prostitutes and young female students during the invasion.
The movie is directed by Chinese director Zhang Yimou. He says he wanted to show the "brilliance of humanity in a circumstance of war" through the dramatic story.
It hits Chinese screens Friday.