It is looking more like the North Koreans are trying to set conditions for a fight along the maritime DMZ in the Yellow Sea:

A battle at sea between North and South Korea is days if not hours away. One way to gauge the accuracy of that forecast is by counting the Chinese fishing vessels in the Yellow Sea. That’s easy enough to do, because they’re almost all gone. That’s the report from Yeonpyeong, the South Korean island that lies less than 15 miles from the nearest land (North Korea) and a few miles south of the Northern Limit Line (NLL). It’s also the island that lent its name to the First and Second Battles of Yeonpyeong, the naval engagements of June 1999 and June 2002. [Global Security Report]

I have covered the 2002 West Sea Naval Battle in depth here at the ROK Drop which ended in a humiliating defeat for the North Koreans, but it cost the lives of six ROK sailors.  The ruling South Korean Roh Moo-hyun government would go on to make excuses for the North Koreans and even imply that the ROK Navy was at fault for what happened.  The wife of one of the deceased sailors was so upset about the treatment of this issue by the ROK government that she left the country.

Here is a map the maritime border and the South Korean islands near it:

A North Korean invasion of one of these islands is another contingency that the ROK Marines that garrison these islands are preparing for.  You can also see how close the North Korean mainland is to the maritime border.  The North Korean Navy was no match for the ROK Navy in 2002 and the capability gap has only grown wider since then.  So it is unlikely the North Koreans will try a naval skirmish again.  As I have been saying here for the past few weeks if the North Koreans try to attack a ROK Naval vessel they will do it using their anti-ship missiles that they have based on the North Korean mainland.

Fully aware of both the threat of an invasion of a South Korean island and the threat of the North Koreans anti-ship missiles Lee Myung-bak is preparing for an overwhelming counterpunch if necessary:

South Korea: Update. The armed forces deployed attack helicopters and K-9 howitzers along the western sea border with North Korea, Yonhap reported 3 June, citing an unnamed military source. The Republic of Korea Air Force said today it is prepared to launch a fleet of advanced fighter jets to retaliate in the event that North Korea provokes a conflict along the western sea border, Yonhap reported. To quote feedback from one expert, the North Korean air force is air pollution.  [Night Watch]

I actually have experience with the K-9 Thunder and they are quite impressive and even better than the US M109 Paladins.   Lee Myung-bak is literally sending the biggest guns he has to defend these islands.  These artillery pieces combined with the ROK Air Force can easily pummel the North Korean garrisons and missile locations along the maritime DMZ.  I fully agree with what Lee Myung-bak is doing because he has to show the North Koreans that any provocation is going to be met with a swift and devastating response that he is serious about executing.  So far I see no hint that Lee is bluffing.