North Korea’s eccentric regime is a close, useful ally of China. Beijing wants a stable North Korea outside of the US-South Korean strategic orbit. China’s most sensitive military and industrial region, Manchuria, is just across the border from North Korea. Any US intrusion into the North would arouse great alarm in China, as it did in December, 1950, during the Korean War.
If a violent power struggle or chaos breaks out in North Korea, Chinese military intervention is possible. Beijing has already issued veiled warnings.
What frightens South Korean strategists the most is not North Korea’s small nuclear program, but rather what they call, "unexpected reunification:" the total collapse of the North Korean state, sending millions of starving refugees south across the Demilitarized Zone. South Korea is in no financial position to feed million or, more onerous, build a viable North Korean. In any event, many South Koreans do not want reunification.
Caution, diplomacy, and tact are required in dealing with North Korea right now, not the kind of warlike, imperial bombast coming from many US Republican candidates. As the Chinese say: "great dangers; great opportunities."
North Korea’s nuclear weapons are not a threat so long as the North is not attacked or invaded. Washington must drop its obsession with this issue and look beyond.