What are the US military doing in South Korea?

Would all-out war between north and south be made more or less likely by a removal of US military bases from South Korea?

• Today's Korea Times headline: "US to fight limited NK provocation". An agreement has been signed, of which the Combined Forces Command (CFC) says, "By completing this plan, we improved our combined readiness posture to allow us to immediately and decisively respond to any North Korean provocation."  The implication seems to be that the South Koreans are somehow not capable of, or inclined to so respond on their own, without US participation.

• Answer:

  I see that this is an old question, but having participated in CFC level exercises with the US forces as a translator to the generals and other high ranking officers, while serving in the South Korean Marines, I have a few points to offer up to the question. In my opinion, the likelihood of an all-out war between NK and SK will increase with the removal of US forces from SK. Even with the presence of USFK (US Forces in Korea), NK wasn't afraid to carry out military provocations, which are done to test the political, military and social responsiveness of SK and US. These actions are always very deliberate and carefully devised. While I was serving in one of the frontline islands, NK carried out the Sinking of Chonan right in front of us, which was done brilliantly in terms of military tactics alone. It really brought chaos to SK's military, politics and the society, and the backlash of that was massive. It was done in a way  that was very difficult for SK to react decisively, because as a responsible member of the international community, it had to collect the evidence of the NK's attack, and the waters in which the attack was carried out had so many natural elements that made search and recovery impossible. By the time, SK did collect enough evidence, the issue has been boiled over and cooled off that a military response didn't make sense. All the while, NK could sit their with their arms folded and watch SK scramble and sweat to deal with their operation. However, NK also is susceptible to miscalculations and Shelling of Yonpyong that followed about 5 months later was a very close call. SK's public would have been ok with its government breaking the Rules of Engagement and conduct aerial assault on NK's origin of attack, were it not for the SK leadership sticking to the rule book and authorize only the allowed level of response by the codes, which were since changed to allow for "total destruction of the origin of threat". In my opinion, US's military presence and involvement in SK definitely has the stabilization effect, because even though SK should be capable of defending itself technically (SK spends 40 times more resources in its military than NK does annually), it makes NK rethink before taking drastic measures when US Army is in Seoul. When we agree that a total war should be avoided at all cost, having US forces with SK forces will have that desired effect in this respect. But also, when NK makes an error and crosses the line to potentially prompting the SK to overpower them, due to the political and social currents in SK at the time, US can act as a counterweight to SK's willingness to fire at will. If SK decides to go to a war with NK, it will drag US into it for sure, so that makes SK leadership think twice before bombing NK. So in a nutshell, I think US presence does have calming effect for both NK and SK, and the SK's willingness to have US force's support shouldn't be viewed as a sign of SK's inability to defend itself against NK, but as stabilizing force in East Asia to avoid unnecessary speculations and paranoia.