missiles with a miniaturized nuclear warhead, that could potentially reach the united states. now, north korea has not yet demonstrated the capability to move a reentry vehicle. that's what would be necessary to get a warhead on to target, down here on earth. but for some months now, wolf, u.s. intelligence, the view, as they've described it to me, is that the u.s. has to assume that north korea has such an untested capability for the purposes of national security here, what is clear is that over the course of these last few months, wolf, north korea has made tremendous progress and it's leading in the direction of a capability that multiple administrations, multiple presidents are said they would never allow. wolf? >> very speedy progress. a lot faster than a lot of experts thought. jim sciutto reporting for us. thank you very much. let's go live to the korean peninsula right now. we're joined by cnn's will ripley, who has reported extensively from inside north korea. he's joining us from seoul, south korea, right now. will, what are you learning?