why did you post as an Anonymous Coward?
DEAD on. and DEAD on what happen to any NK sub where the US doesn't want it. Gone, without a word, with all hands.
This is 2016, not 1942. The technology for detecting and tracking submerged vessels has improved somewhat in the last 74 years. The North Korean subs are basically vintage 1960s era technology, like much of the rest of their military. They're not going anywhere without being tracked and if they approach the United States they will be sunk, war or no war, because nobody will be watching except the ones doing the shooting. Submarines can be accident prone and the Pacific Ocean has a fearsome reputation among mariners. Nobody would have any problem believing that a North Korean submarine had an "accident" while at sea. In fact, the visibility of submarines at sea to the general public is so low that they United States could essentially deny any knowledge. Finally, the North Koreans are so unsympathetic and unpopular these days that nobody would care what happened to their submarine anyway.