Thinking the North are scared that the south will strike or invade during one of the military exercises and probably why the posture or rhetoric. Too bad that US has to be on one side of a potential civil war, but its possible that political solution leading to re-unification could still happen. Having said that there are tremendous differences in ideology and maybe they cannot get it together. But if the north does away with the hot line and something dumb like shelling of a South Korean village happens again, could start a very bloody war, and if so 20 years after it will be all good with one Korea and tourism industry etc, but it would have been a terrible price the Koreans north and south had to pay. from a distance its looks pretty dumb for those guys to go to civil war, but it could happen.