This new Chinese feature film about how the Japanese Imperial Army raped and razed Nanking in 1937 is relentless, masterful, and important. But it joins that class of movies—Shoah, The Sorrow and the Pity, The Cove—that some people feel morally compelled to watch but that no sane person "enjoys." The events in Nanking, which some Japanese officials still try to soft-pedal, were so horrible, they reduced Nazis to tears. Specifically, a Nazi named John Rabe who tried to set up a refugee zone in Nanking where the Japanese Army couldn't charge in, casually chuck babies out windows, laugh while hanging everyday Chinese people from street lamps with barbed wire, and commit other brutalities I don't even have the stomach to describe. It's as if a cloud of evil touched down in Nanking and temporarily unleashed the latent psychopathology of an entire army.

Rabe leveraged every bit of Nazi cred that he could to keep Japanese soldiers out of the refugee zone—but it didn't work. At one point, Japanese leaders came to Rabe and said, basically, Loan us 100 young women from your refugee camp for a 48-hour all-army orgy at our designated rape palace or we'll come in and make you wish you had. That's the moment (in the film at least) when you see the old Nazi weep. Of those 100 or so women, many died or went mad within 48 hours of being handed over to the Japanese Army.

The fact that director Lu Chuan takes us inside the rape palace—and many other hideous places—to bear witness is discomforting. That he takes us there with such technically graceful black-and-white cinematography, sparse dialogue, and an uncanny ability to find deep emotions in his actors' smallest facial expressions (a twitch of the lips, a look in the eyes) is devastating. Also devastating: the great human relationships forged among the Chinese refugees and their foreign advocates, mostly Germans and Americans, working together to slow the Japanese Army's horror show. Chuan zooms from small gestures of tenderness to large-scale viciousness.

The City of Life and Death is an excellent—but searing—film. Proceed with caution.