Allow me to generalize the differences between the enemies in the Pacific Theater and the European Theater into a form that every gamer should comprehend:
Germans = Protoss
Japanese = Zerg
Relative to the Americans and even ze Germans, the Japanese had very little respect for human life. Your honor and the overarching objective of winning the war were paramount, even if it meant self-sacrifice.
The Japs thought that they could apply such principles to POWs (and everybody they conquered in general), and thus their was a huge uproar of vengeance when Americans learned of the conditions their captured soldiers were being subjected to (There was so much uproar that a good chunk of the missions behind-enemy-lines Americans undertook in my country involved saving diseased, malnourished, practically dead POWs before they could be executed by retreating Japs.) Even though the Japs would willingly subject themselves to such conditions if their honor was at stake.
If they pull this off right, there won't only be a change in scenery (My guess is that it will involve a lot of island hopping, as in more amphibious and airborne assaults) but a change in gameplay as well.
"Nothing livens up a robotic hymn of doom more than an amazing pair of jugs." - Brak