Bill Guttentag and Dan Sturman’s 2007 documentary has all the makings of a valuable and important history lesson but lacks a viable form for combining its diverse elements. Its subject is the horrific Japanese attack on the Chinese capital in 1937 and ’38; the elements include newsreel footage, interviews with Chinese survivors, and selections from the diaries and letters of Westerners who witnessed the events and tried to intervene (performed by such actors as Woody Harrelson, Mariel Hemingway, and J