well if u ask me.... North Korea will not start world war 3. They definitely wont bomb the south or Japan becauise America would just blow North korea into nuclear dust. Most likely some other super country would start a third world war. But right now i dont think the north is of any threat since they arent much of a military power since the korean war and they dont got much nuclear power as tehy just tested their first nuke recently. So expect world war 3 to happen in about 10 years. right now there is a very low possibility mainly because the north doesnt have the guts to mess with any country that has more military strength. If they team up with China maybe... but right now i dont think so.