In a study submitted to the US Senate’s Armed Forces Committee, the Center for Strategic and International Studies recommended, among other things, the deployment of US Marines to help defend South Korea’s West Sea islands:
There is also increased ROK interest in expanding the USMC presence on the peninsula because of weaknesses in the ROK Marines‘ capabilities to manage West Sea contingencies as revealed in the Cheonan and Yeonpyeong attacks. The utility of USMC training also increases because possible North Korean use of WMD in the central front puts a premium on deep sea maneuver from the sea in any warfighting or instability scenarios. Currently, U.S. plans put the USMC presence on the peninsula at less than 200 troops. In South Korea, brigade-size exercises and combined arms training that cannot be conducted elsewhere in the region are possible. The project team found that senior ROK leaders are open to expanding the USMC presence for exercising, particularly with ROK Marines near the northwest islands (where the Cheonan sinking and Yeonpyeong island shelling occurred). Currently Mujuk (on the east coast) is the base allotted for Marines as part of LPP, but Camp Casey at Tongducheon, which has traditionally been home to two maneuver brigades, is another possible area for exercises. Under LPP, Camp Casey is scheduled to be returned to South Korea, and use of the facilities would require renegotiation (which may not be as hard as it sounds given the lack of new plans or investment by local officials for after the handover). Gwannyeong port also has potential as a staging area for Marines. In addition, the ROK government is building a new naval base on the island of Jeju at the southern tip of the peninsula. However, despite an apparent ROK willingness to expand exercises and some logistical support for more regular USMC engagement on the peninsula, there is not much political support in Seoul for permanent basing of a MAGTF comparable to that planned for Northern Australia, unless it were dedicated to the deterrence mission on the peninsula.
This is me after reading that:
Read the rest of the report on your own—especially if you’re a policy wonk-type.