From The BBC:
The Cheonan sank after an as yet unexplained blast on 26 March
South Korea’s defence minister has said those responsible for the deaths of 46 sailors on board a warship that sank after an explosion must “pay a price”.
Kim Tae-young promised “punitive action” against “the perpetrators who killed our soldiers.”
He did not specify what form this could take. South Korea has not directly blamed North Korea – and Pyongyang has denied any role.
The Cheonan sank after a “close-range” blast that split it in two.
>Last month, a mass funeral was held for the 46 sailors, including six whose bodies have not been recovered.
Aluminium fragments
Many South Koreans believe North Korea sank the ship, correspondents say.
We should deal some kind of blow against those forces which made our officers and men sacrifice their lives 
>Kim Tae-young
South Korean Defence Minister
What if North Korea was to blame?
The ship has been salvaged from the sea bed and is being examined by an international team of naval experts trying to find out what caused it to sink close to the North Korean border on 26 March.
The South Korean defence minister has said a torpedo strike is among the most likely causes.
So far the investigation team has said only that they have found evidence of an underwater explosion and it is not known whether fragments of any weapon have been discovered.
Mr Kim said officials were scrutinising pieces of aluminium, a key material in making a torpedo, that were picked up from the disaster area.
“I believe that, by thoroughly and completely getting to the bottom of the incident to the maximum extent possible, we should deal some kind of blow against those forces which made our officers and men sacrifice their lives for their country,” the defence minister said on KBS television.
North and South Korea are still technically at war, since the 1950-53 conflict ended without a peace treaty.
Over the years there have been several naval clashes off the west coast of the peninsula, in the area where the Cheonan went down.
Trying to put myself in North Korea’s shoes. What point did this service killing these sailors?
1. North Korea is the worlds largest prison, except that the prisoners have no rights. In fact, the average height of a North Korean, is inches smaller than the height of a S Korean, because of the lack of nutrition.
2. Kim Jung Ill, the leader of NORK is very ill, and will die anytime. He probably actually feels very bad as well as being certifiably insane. We are talking about a man who had his people build him a private highway for use by he and his sons alone, while his people are rewarded for slavery, by starvation.
3. Therefore, it is my guess, that he wants to take a few million people with him when he dies, to add to the glory of his name. as that would fit the exact logic of the rest of his life.
No doubt Obama will be completely incapable of understanding this, and aid and abet his plans wittingly or no.
And so it begins…
North Korea has strong ties with Iran and other anti-western regimes.
If North Korea also has ties to any Muslim countries south of the penninsula (Malaysia or Indonesia, for example), then South Korea would be forced to fight a war on two fronts, instead of only to the north.
Either way, this will erupt in another war, which, as one commenter mentioned above, really didn’t end.
May South Korea free the people of the north and rebuild it.
Imagine German reunification, except the East Germans hadn’t had a proper meal or night out in 3 generations, and had no usefull skills.
I suspect South Korea is terrified at the notion of attempting to absorb X-millions of starving brainwashed zombies, which the current dictator and his father have created