WHY WE CAN'T INVADE NORTH KOREA: Patrick Ruffini e-mails to ask:

"Why shouldn't we go to war with North Korea, not now, not next year, but if and when we're ready? Why shouldn't we simply declare that the existence of the the persistence of the DPRK's regime is not in the national interest of the United States, and therefore, we
are adopting a policy of regime change?"

I actually answered this question back in October; here's the key part:

"Why, then, is the U.S. going after Iraq while 'consulting' on North Korea? It’s not because pre-emption can’t apply to both countries; it’s because the power politics of the Middle East are radically different from those of the Far East. Invade Iraq, and no other great power’s sphere of influence is dramatically affected; the Middle East will remain an American bailiwick for quite some time. North Korea borders China and Russia; a pre-emptive attack against Pyongyang understandably ruffles more feathers."

To expand, imagine that the U.S. pursues regime change. Forget the claims that the DPRK army numbers a million -- let's assume that North Korea could be conquered in less than three months. The political and economic fallout would nevertheless be enormous. North Korea borders both China and Russia, and they'd be as happy with an invasion as we would be if either of those countries decided to conquer Mexico. Such an act would undoubtedly trigger the security dilemma, lead other capitals beyond Moscow and Beijing to ally against us in the long term. [But why wouldn't China and Russia bandwagon in the face of U.S. might?--ed. Here's where I part company with the neocons and agree with the realists. Vulnerable Middle Eastern regimes may choose to bandwagon when faced with U.S. power projection -- though this book suggests otherwise -- but China and Russia are not going to appease a country that invades one of their neighbors without any accomodation to their security interests].

The impact on the Korean peninsula would also be devastating. The geographic proximity of Seoul to North Korean artillery means that, regardless of whether Pyongyang has a functioning nuclear weapon, they can engage in mutually assured destruction. It would take South Korea at least a generation to overcome the damage to their capital, plus the costs of assisting the economic wasteland that is North Korea [C'mon, how expensive could it be?--ed. In 1995, the DOD estimated the costs of a ground campaign on the Korean peninsula to exceed $1 trillion; the U.S. would have to pony up at least $100 billion. Oh, and the casualty estimates range from 80,000 to 100,000 U.S. casualties, and ROK casualties in the hundreds of thousands].