One thought here, before I bow out (don't like how people argue on here:P).
Tenchu, I actually agree with you on your opinions of human nature: it's the same and it's bad. I also agree that no country lasts forever, and the U.S. is no exception. But do those facts entitle us to sit on our hands while others make the most of their nature and do horrible things? Does it mean we should just lie down with paper bags over our heads and wait for the world to end?
I don't think so.
Human nature can be effectively restrained to a point, by good government. You're really making me think you don't believe in human rights, or something--in the name of preserving innocents, you seem content with the idea of oppressive governments and bloodthirsty tyrants taking over however much of the world they please--and those types don't build daycares. War is horrible. It's full of all sorts of evils. But there
are times when you do have a choice to choose the lesser of two evils, and effectively work to bring good out of it.
As for the actual topic...yes, I think if China and North Korea become a real threat, Japan will need a military. Hopefully we won't find it turned on us again.:P I don't really see the point of our military bases in Japan, except I imagine they are useful for monitoring N.K. since they are pretty close. If they also help to cement the friendship of Japan and the U.S., they are not a bad idea...but that doesn't often seem to be the case.