Re: Spartan Hoplite v Samurai...
Simple, the spartans would set up their phalanx and start marching towards the Japanese. If the Japanese tried a frontal assault those taking part would be slaughtered. Learning from this, they would divide their forces and use their mobility to transfer a large amount of their forces to the Spartan flanks and rear. If the Spartans remain in their original phalanx then they would be slaughtered by the flanking forces. If they formed, oh say, a square formation, the Japanese would pepper them with arrows until they were weak enough to engage in melee combat.
This is assuming it would take place on a flat field. Obviously terrain could be a major factor as well. If the Spartans were facing the Japanese in a confined area, in which the borders of the battlefield was comprised of impassable terrain (a river, cliffs, the like) the Spartans might be able to trap the Japanese against the front of the phalanx and slaughter them. In most cases considering the terrain, the Japanese would win, due to the superior flexibility of their forces, the exact same reason why the Romans were able to conquer Greece.