We hear that the reason that North Korea is developing their missile and nuclear capabilities is to insure their own survival. However, if one believes that the past events can be a means of predicting future events could there be another motive for North Korea's actions.
We know for a fact that the invasion of South Korea by the North in Jan of 1950 was predicated on the concept of unifying all of Korea. We also know that the North still has this as one of their objectives. We also can assume with a fairly large certainty that South Korea will never accept the idea of being ruled by the government of North Korea. Now whether Kim accepts this is a matter of conjecture. If so the only possible way for him to reunite Korea is by force. If so could Kim make the assumption that he can invade the South and not be thwarted is by holding the possibility of a nuclear strike on those that would oppose his act?
Now it appears that I am not alone in the above assumption. (happened to run across this while looking up information)