i'm jon scott. nuclear north korea trepbgt the u.s. with physical response to our naval exercises with south korea this weekend. the north is accused of sinking a south korean warship in march which called for sanctions against the rogue nation. let's talk about it. physical response, michael, what are they threatening here? >> the truth is nobody knows. back in march the reason we are having this crisis, back in march they sung a south korean navy ship and murdered 46 sailors. since then they kept their head down as they usually do after they do something provocative. we have waited a number of months to send in some ships to have naval exercises. the north koreans say if we do it there is going to be a ph- physical response. i don't think they are going to try to take out any ships, but there are other things they can do in terms of attacks.