Go to sfgate to read an article about Ken Watanabe, the ‘Samurai guy’!
A little and funny piece from it:
Watanabe needed all the strength he could muster to enact “Samurai’s” grueling battle scenes, which required two months of filming in New Zealand. He yelled himself hoarse as the “commander” of 500 extras, but when Watanabe was in good voice, he and Cruise shared some very special song-and-dance moments.
“Those scenes we had to do many times, charging on the horses. In between, I’d go sing ‘Close to You’ by the Carpenters, and Tom would join with me. Then we go back to the set and get on horses and yell, ‘Arrrggghh!’ “

Ha ha ha ha ha ha ha!