Though he is known for being daring and athletic both onscreen and off, Tom Cruise's star turn in the upcoming film "The Way of the Samurai" was one of the most difficult roles he's ever played, the Associated Press reports.

In this period film, scheduled for release on December 5, Cruise, 41, plays an American Civil War veteran hired by the Japanese Emperor to school his warriors in Western warfare tactics, but who becomes increasingly fascinated by the samurai.

"I trained for eight months prior to shooting the film," Cruise said during a packed news conference in Tokyo yesterday, according to AP. "I put on 20 pounds for the character but also for the muscle to carry the swords and wear the armor."

The superstar's Japanese co-star Ken Watanabe, a familiar face in Japanese Samurai films, told the crowd that Cruise was a quick learner. "I feel like we have been through a battle together," he said.

The $114 million action film, directed by Edward Zwick, shot in New Zealand for four months. Filming wrapped up in May.

"This is very personal to me," Cruise said of the film at the news conference. "I strongly believe in the (samurai's) values of honor, loyalty and compassion."