Tormented Civil War veteran Capt. Nathan Algren is coerced by a mercenary officer to train the Japanese Emperor's troops in the use of modern weaponry. Opposing this modernization are the samurai warriors who are holding fast to their traditions of honor, despite their strategic disadvantage. As a captive of the samurai leader, Algren learns, appreciates, and adopts the samurai code, switching sides for a climactic battle that will put everyone's honor to the ultimate test.