Very good. In particular, the film does a good job of communicating the uncertainty of the characters to the viewers. Why has the attack stopped? What are they doing now? The characters don't know, and neither do we. Well done.
The Wikipedia article on the film discusses how the film deviates from the actual history.
The film opens on a mass wedding ceremony.By the end of the film, the officers ("a chap ought to look smart in front of the men") are showing signs of the battle.The film ends on not so triumphant a note, with Chard standing alone among the dead.