How many troops are enough to represent our commitment? No one is advocating a total pullout. Rumsfeld wanted to reduce the level from 37,000 to 25,000 now and perhaps down to 12,000 to 13,000 down the road. We need the bare minimum there so we can address real needs elsewhere. Commitment is a euphemism for trip wire troops.
Having forces on the Korean peninsula is also crucial to security strategy in the Far East as a whole. The peninsula has always been the lynch pin to the region. It borders Japan, China and Russia. All three of the countries are hugely important to our national interests. Out forces in South Korea put us right in the middle of the region. If China becomes hostile, we have military bases a very short air flight away from their industrial region. Bases in South Korea give us options and leverage in the Far East as a whole.
We have bases in Japan. If we were in a big time shooting war with China, our bases in Korea (with 37,000 troops) would not be of any real use and our air bases would come under attack. I wonder if the Koreans would want to be drawn into a shooting war between the US and China, if for example, China were to attack Taiwan.
We could always set up skeleton bases in Korea that could be rapidly built up in time of crisis. Tying down forces needlessly doesn't contribute to our overall defense posture. We need to look at our force levels around the globe in terms of our overall strategy and threat assessment. Flexibility is key.
When you throw in our large economic ties with South Korea (anyone own a Samsung cell phone?) and the fact that there are usually 50,000 American civilians in South Korea--most of them in Seoul--the picture is clear that we cannot leave South Korea. It would be tantamount to shirking our nation's duty to protect our citizens lives and livelihoods.
You don't station large numbers of troops to protect American citizens working overseas. We have 30,000 Americans working in Saudi Arabia. The number of Americans working overseas is well over a million.