Can anybody break this down for me? Knowledge of Japanese culture required.

Ok, so I’ve been putting off going to bed because I’m watching a movie and occasionally checking Fluther. The movie is City of Life and Death, and it’s about the rape of Nanking.
I’m nearly to the end when this scene came up. I find it utterly entrancing, and stirring despite the context.
I’m sure that each movement of the hands means something, each step, and even the posture of the dancers. The drums, as always, awaken something entirely primal within me and I’m sure that there are very sound psychological reasons for using the drums in specific occasions.
I’d like to see more of this type of dance, but you tube is not coughing up much. I would also like explanations of the movements and what they are shouting if anyone happens to know.
Any information would be greatly appreciated by me.