I think there is alot of people who seem to under estimate the capabilities of North Korea due to the poverty and economic issues plus the age of their weapons platforms. Neither China, U.S or ROK forces are going to enter that country without suffering a major loss of life, we should not forget that North Korea has been at a state of war with ROK now for quite some time, they have gun positions laid out in the sides of mountains, some of these systems actually have elavators that can move weapons from one position to the other as an example, now as a added bonus they have nukes and they would not hesitate to use them if cornered. With the terrian that would be fought over it really is not ideal for armored penetrations, artillery and ground pounders will rule that fight with tanks providing indirect fire support, for this the only edge that I see will come in the form of air and naval assets. Would any of the big three eventually win that fight yes, but with the amount of bloodshed and destruction that would happen it is just not worth the risk from a dedicated enemy opponent like North Korea. Most likely approach is to let this hungry tiger die from the inside out, then will come the issue between China and South Korea on how this will be handled properly, China will have to walk lightly with the ROK because of the size of their economy and military and due to ROKs friendship with the U.S.. I have talked to ROK officers over dinner and drinks and have asked them who they felt their future enemy would be and the majority of them felt that it will be China, as a surprise they never mentioned Japan as a future threat and felt that they should have more of a military cooperation with them, even though they do not trust them, they actually have learned to not trust anyone. just my two bits that i would like to add.