Or so they claim, and judging from the latest quake from their test on Sunday they probably do. If an H-bomb were dropped on Seoul, some two million people would be killed. Greater devastation would be wreaked on Tokyo and Los Angeles.
North Korea is Exhibit A in the limitations of the rational actor school of foreign relations. That posits that foreign policy should be based upon the belief that the foreign policy of other states can be understood, and better dealt with, by assuming that the leaders of the state are rational. Two problems: even a cursory study of history reveals that some leaders of nations have not been rational, and rationality in any case, like beauty, is in the eye of the beholder. This is not going to end well, especially for the people luckless enough to be born in North Korea.