Actually, not a whole lot. Mostly, it just reinforced stuff we already know. I said the same thing after the Cheonan was sunk earlier this year.
1. Koreans take this stuff in stride. It was more the international media that portrayed this as a major crisis. In Korea, everyone went about their regular business. The stock market didn’t drop. There was no rush on food-stuffs in grocery stores. No one is digging bunkers. It’s not evolving into the Cuban Missile Crisis. The Korean media reported rather well on the crisis, without the level of overstatement – ‘Korea on the brink of war!’ – that was common from the international media in the first few days especially. This is far from the worst crisis with NK in the history of the stand-off.
2. These sorts of things re-galvanize the flagging US-Korea defense relationship. This may be the biggest benefit to South Korea from the whole mess. Although US political and military figures regularly invoke the alliance as shoulder-to-shoulder (which of course you would expect them to say) both here and in the US, the reality is that the American position here is shrinking and moving away from the hot-spots under substantial US budgetary pressures at home (a $1.3 trillion deficit!). USFK (US Forces in Korea) has shrunk substantially over the years. US nukes are out. The Combined Forces Combined (CFC) is schedule for termination. The number of bases has shrunk. The US is no longer deployed along the DMZ (the big bases will be around Pyeongtaek, south of Seoul, in the future). The massive US fiscal mess will make it even harder to retain what we still have here. Defense budget cuts are coming – in a big way if we want to save Medicare, Medicaid, and Social Security – and US overseas deployments are an obvious place to cut (Iraq, Afghanistan, Korea, western NATO especially, unless the hosts want to pay 100% of the costs – which option the Koreans should genuinely consider as a part of point 3 below). Here is my fuller commentary on this. Also here and here.
Korea particularly is a tempting place to cut. Korea is wealthy and has a capable military. It can afford to spend even more on defense (below), while the US most certainly cannot. Nor is Korea really a core US defense interest. Unification on Northern-terms would have little impact on the US now that the Cold War is over; Korea is more a regional issue now, not a global one. Korea hardly ranks against Japan, Canada, Mexico, (Israel?) or Western Europe as obvious ‘core commitments’ to American security. This does not mean I want the US to abandon Korea, only that the likelihood is growing, because the costs to the US of an ROK defeat/reduction are low for the US. Nor do Americans really want to fight in Korea (only 41% now), especially after all the misadventures of the 10-year war on terrorism. Read this as well on this issue.
So if you are Korea, these sorts of scrapes are secretly valuable from a medium-term national defense view. They put NK back on page 1 for the US voter. They force the US to say yet again in public, that the US will defend Korea. This creates greater ‘audience costs’ for US elites should they try to slip out of the alliance commitment in the future. After the Cheonan, the dissolution of the CFC was delayed for 3 years. Note here that Obama talked around Barbara Walters’ excellent question, ‘is an attack on SK an attack on the US?’ The president ducked that one (video above). These kinds of public comments make it harder for the US to retrench (even though we really need to), and that is good if you are SK.
3. SK needs to spend more on defense. SK only spend 2.7% of GDP (according to the CIA). I hate to sound like an uber-hawk, but honestly, that is really not enough if you live next to NK and are number one on the hit list. By now it should be clear to almost everyone except the most unreconstructed SK leftist, that dealing with NK is only possible from a position of strength. The North cheated a lot during the Sunshine Policy years, even demanding a big cash payment for Kim Jong Il personally to get him to attend the inter-Korean summit. And in the last few years, the North has gotten even nastier – with the nuke and missile tests and more of these sorts of asymmetric strikes. But Koehler has a series of good links and analysis here that SK has not adjusted well. The US is broke; SK is not. The time for burden-sharing is here.
But you say this is just arms racing. Everyone will just run faster and faster to stay in place. More Southern weapons will scare the North into further wild behavior and yet further punish the much-suffering NK taxpayer. Maybe, but the NK military functions as a state-within-a-state already, and its stringencies on the NK citizenry derive as much from its internal as external insecurities. And NK policy-makers are so irresponsible (Brzezinski went so far as to call them insane), that the causal connection between lower SK defense spending and better NK behavior seems loose at best, while the costs – like the Cheonan and Yeonpyeong – are very clear. Among other things, South Korea might want to consider militarizing more areas north of Seoul and depopulating them gradually, expanding the navy, as these flashpoints occur mostly in the Yellow Sea, paying for more of USFK, even for its expansion, conscribing women as well as men (as Israel does), and possibly – I hesitate to say – signaling renewed interest in nuclear weapons. That last one is hugely controversial, but given the growing likelihood of US retrenchment and the expanding Northern nuclear program, it should probably be discussed.