Trivia: In scene 32, Katsumoto and Algren ride through the line of troops and as Algren dismounts, his horse kicks out at the soldier to the right of the camera and hits him in the groin. The soldier bends over with the impact, backs up, then bravely straightens up again as the scene continues. (01:53:55)
Trivia: While Hiroyuki Sanada was filming a battle sequence with Tom Cruise (Nathan Algren), a "live" sword was used. The mechanical horse prop in the sequence broke, and Cruise did not fall off as planned. The sword came within an inch of Cruise's neck. At the time, bystanders and crew screamed, almost witnessing the actor's decapitation.
Trivia: All the ninja seen in the film were played by actual modern day practitioners of the ninjitsu arts. Allegedly this led to a running joke on set where if the ninja were rehearsing with a stunt double or an extra they would spontaneously perform a kill move (obviously stopping before actually hitting their opponent) then remind everyone they were only contracted to let Tom Cruise live through the movie. Everyone else, as far as they were concerned, was fair game.
Answer: The Battle of Thermopylae, see http://en.wikipedia.org/wiki/Battle_of_Thermopylae for more info.
Myridon