(Again, presuming this was a NK sub) S. Korea is backed up against a wall here. They will have to do something, otherwise the current gov. will find their rear ends in the streets and maybe hanging from lamposts.
And I don’t think a token response is going to do. NK just sunk a major SK naval vessel and it sounds like upwards of half the crew (50) may have died. This is no minor incident. In fact, this may be the largest security incident in the Korean theater since Korean War hostilites ceased.
We (Obama that is) may sit on his hands. But the S. Koreans don’t have that luxury IMO.
probably will bomb the port where the sub presumably came out of.