In the beginning, Pyongyang's ability to appear ferocious was limited to the North Korean army's power to shell Seoul. It had massed artillery along the border and could theoretically devastate the southern capital, assuming the North had enough ammunition, its artillery worked and air power didn't lay waste to its massed artillery. The point was not that it was going to level Seoul but that it had the ability to do so. There were benefits to outsiders in destabilizing the northern regime, but Pyongyang's ferocity -- uncertain though its capabilities were -- was enough to dissuade South Korea and its allies from trying to undermine the regime. Its later move to develop missiles and nuclear weapons followed from the strategy of ferocity -- since nothing was worth a nuclear war, enraging the regime by trying to undermine it wasn't worth the risk.