There are many dynamics at play here, but North Korea is certainly playing a very dangerous game.
Evidence that NK sank the South Korean ship seems to be forthcoming. And North Korea has forced all South Koreans out of the joint interactive area. And of course there is the obligatory NK threat of total destruction of SK.
This is exactly the situation that could be set off by mistake when both sides are already tensely watching everything.
http://www.bangkokpost.com/news/world/179243/n-korea-makes-new-threats-as-tensions-riseS.Korea to punish N.Korea despite threats
"South Korea vowed Wednesday to punish North Korea for sinking a warship despite fiery threats from the communist regime, and the United States said the world must respond to the naval attack.
After North Korea said it was severing all links with the rival South, its military said it would block access to a joint industrial estate if the South resumes loudspeaker propaganda broadcasts across the tense frontier.
A multinational investigation concluded last week that a North Korean submarine had torpedoed one of Seoul's corvettes, the Cheonan, on March 26 with the loss of 46 lives. The findings sparked strong international condemnation of the hardline communist state, but the North's ally China was a notable exception.
The South Monday announced a package of reprisals, including a halt to most trade. It is also mounting a diplomatic drive to punish the North through the United Nations Security Council."
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