A South Korean politician has provided a small intel dump regarding the situation just prior to the sinking of the Navy corvette Cheonan.

The Navy corvette Cheonan was warned on the morning it sank on March 26 that a salmon-class North Korean submarine and support ships had disappeared from their bases the day before, a lawmaker claims.

 

Democratic Party lawmaker Shin Hak-yong on Monday said on the morning of the North's attack on the Cheonan, "warnings were given by the Second Fleet Command that a salmon-class North Korean submarine and support ships had been out to sea for unknown operations. Right before the Cheonan was attacked, all artillery guns on the nearby North Korean coasts were found to be combat-ready. But despite these rapid movements of the North Korean military, neither the Joint Chiefs of Staff nor the Second Fleet Command took appropriate measures."

The article is a very interesting read.

 

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The Navy corvette Cheonan was warned on the morning it sank on March 26 that a salmon-class North Korean submarine and support ships had disappeared from their bases the day before, a lawmaker claims. Democratic Party lawmaker Shin Hak-yong on Monday said on the morning of the North's attack on the Cheonan, "warnings were given by the Second Fleet Command that a salmon-class North Korean submarine and support ships had been out to sea for unknown operations. Right before the Cheonan was attacked, all artillery guns on the nearby North Korean coasts were found to be combat-ready. But despite these rapid movements of the North Korean military, neither the Joint Chiefs of Staff nor the Second Fleet Command took appropriate measures."

 

The info about the DPRK submarine being absent from its berth was, iirc, already known and publicly disclosed back in March, following the sinking. The bit about the artillery being manned and ready is interesting but I understand that these (or nearby) batteries regularly conducted fires into the ocean in that broader area. I am not sure that either piece of intel could have helped Cheonan.