North Korea may well be a dangerous state with an unstable leader but neither the regime nor the nation is suicidal. There may be a large military but it simply lacks the resources to mount an invasion.  The occasional demonstrations of military prowess have far more to do with negotiations about aid than they have to do with a genuine military threat to the South.  It is inconceivable that North Korea would take any significant military action without the agreement of Beijing and it is inconceivable that any military action would achieve more than a gnat bite from the point of view of either the American or Chinese military. Although Kim Jong-Il may be a master of sabre-rattling as a form of brinkmanship it is staggeringly unlikely that the sabre would ever be unsheathed.  It is worth noting that the idea that Pyongyang would commit financial suicide by attacking their main form of financial support – South Korea – is relatively ridiculous. The shifting relationship between the two Koreas has more to do with the varying level of political machismo in Seoul than it has to do with the realities of the possibility of military intervention or confrontation.