hitting guam is the latest provocation. abc's martha raddatz reports from seoul. >> reporter: the u.s. is tracking a mobile missile launcher that has been moved within north korea by train. the launcher has the ability to strike japan, as well as u.s. bases in okinawa and guam. adding to the fears the young leader of the north said the moment explosion is coming. north korea news readers, promising a justified all-out war. while here in south korea u.s. forces trained in hazmat suits. preparation in the unlikely event kim jong-un were to deploy his nation's arsenal of chemical weapons. one of the largest stockpiles in the world. but of the only attack so far, a