North Korea is flexing its muscles, again. The UN imposing further sanctions onto North Korea in a (late) response to its December 2012 missile and February 2013 nuclear tests had the regime in Pyongyang go ballistic leading to angry rhetoric and threats to attack the US and its allies with ballistic and nuclear weapons.
While due to technological shortcomings such threats (fortunately) lack credibility, Pyongyang's conventional and probably more so its asymmetric military capabilities do nonetheless pose a potential military threat to South Korea and its neighbors. Massive artillery systems stationed along the DMZ, the country's 200.000 Special Operation Forces (SOF) together with regime's ambitions to boost and modernize the country's its naval capabilities and aircraft will continue to make sure that South Korean, US and Japanese armed forces will stay on high alert in the months ahead. An all-out war triggered by a North Korean pre-emptive attack on the other hand can most probably be excluded: while Pyongyang would be able to inflict heavy casualties and damage on South Korean territory during the (very) early phase of such an attack, allied bombing would be massive leaving little left of Pyongyang and the regime in a few weeks.
For the time being, be prepared for the occasional shelling of or intrusion into South Korean territory as well inter-Korean small-scale naval clashes in and around disputed territorial waters.