I need help finding out the name of a samurai movie I saw in the early 90s.

From what I remember, there was a samurai teacher, he had a caucasian student and japanese one (not sure if he was a student or just a rival), the caucasian student was an obedient student but less experienced than the Japanese one who was not, and who was actually evil.

In one of the scenes, the caucasian student is buried in the ground up to his head, punished? I guess for some reason, I don't remember. I think he hallucinates while in this situation or eats a bug, not sure.

In the last scene, the teacher was going to fight against the evil samurai (student?), but was shot by some bad guys and the caucasian student took up his teacher's sword and fought against the evil samurai, he was outmatched but eventually won.

Would appreciate it very much if someone could tell me the name for this one.

Thanks

The Challenge (1982) (http://www.imdb.com/title/tt0083726/)?
From NEW YORK TIMES review:

As part of his indoctrination, Rick spends five days buried up to his neck in the sand, while Mr. Mifune's helpers place unattainable bowls of rice beside his face. When this makes him hungry enough, he eats whatever beetles he can catch on his tongue.

Thanks, now I can rent this movie