North Korea's military strategy is built around retribution. If South Korea and the US were to launch an attack on North Korea they would eventually win, but th

North Korea's military strategy is built around retribution. If South Korea and the US were to launch an attack on North Korea they would eventually win, but the costs in military and civilian (both North and South Korean) casualties would be so extreme as to make it not worthwhile. As an example: North Korea has thousands of artillery pieces positioned near the border, which are capable of striking targets fairly deep in South Korean territory. A number of them can strike into Seoul. And they are situated in tunnels in the side of mountains, well stocked with plenty of ammunition. The artillery pieces stay in the tunnels, pop out to fire a round, and roll back in to be reloaded. They can fire into high population areas and can hit a number of important military installations near the border. Plus, North Korea is able to produce chemical weapons, and is believed to have chemical artillery rounds stockpiled. Estimates are that it would take a South Korean-Japanese-US combined air force weeks to find and neutralize all those positions. You also have some fairly rough terrain in North Korea, which is not very suitable to large-scale armored and mechanized assaults. Any invasion would also have to face a population that has been indoctrinated for generations to hate and fear South Koreans, Japanese, and Americans. Long range cruise missiles like these give the North Koreans additional options for retribution against such an attack. There's even speculation that North Korea may implement nuclear landmines, essentially placing nuclear warheads near the border to be detonated if an invasion were to overrun that position. In short, any potential invasion or regime change of North Korea would be a very long and very bloody affair, unless there are some serious changes in the status quo. Which is exactly what Kim Jung Un wants. He doesn't have any real ambitions to re-unite the Korean peninsula, or to liberalize the nation and re-enter the world stage. His only goal is maintaining power, which is exactly what this is.