The Flowers of War is a movie based on a novel originally titled 'The 13 Flowers of Nanjing' by the Chinese American author Geling Yan. The novel is based on true events in that it is centered on the 1937 Japanese attack known as the Massacre of Nanjing (sometimes spelled Nanking at that time.) The attack became one of the most infamous stories from the Japanese invasion of China, as both soldiers and civilians were killed in huge numbers - it is estimated that out of the city's original population of 600,000 half were killed in less than two months.

Both the film and the novel portray some of the horrors that took place, though probably no fictional account could give a full picture of these. Some people escaped and others tried to help - among these were some Americans, including Christian missionaries, who tried to protect some civilians, so this part of the film and novel also has a historical basis.