The back ground of the film sets in an intricate period of history in China but the point of the film isn't about the struggles nor the ignominy that the Chinese people had to endure in that time. The film only shows a glimpse about those things. I think the setting is made to emphasize the loneliness of an individual in front of the flow of history and how the idealism ruins the innocence, enthusiasm and patriotism of those young adults who want to make a change.
And throughout the story off two different people who are opponents and hate each other but still can comfort the other's sorrow, loneliness and emptiness to the point that they finally fall in love, I think the message that the movie wants to demonstrate is that we human may be different in race, in gender, in society status, etc. but after all, we will always have the empathy or connection to one another as long as we open our hearts and truly listen to them.
Beside the excellent screenplay and acting of the cast, the cinematography of the film is marvelous. It does not only successfully capture the doleful and fragile beauty of Shanghai in the 1940s but also gives out the vibe of a melancholy collapse of the youth delusion.
The film might be a little too long with the slow pace in the first 45 minutes and probably put you out of your comfort zone, but if you are patient with it, you would find the true gem.