North Korea has conducted two underground nuclear tests despite repeated warnings from US and Japan. The North Korean regime has been taking aggressive posture in the last two months. First it tested a long range missile under the guise of a satellite launch.
Later on it sent out the UN nuclear inspectors out of its country and also started production of missile grade uranium. Now it has widened the gap with the US / Japan / South Korea , by going in for two under ground nuclear tests.
There are experts who say that North Korea is working under the guidance of China, which wants to reassert itself in the world order. It is better for China to use indirect ways of improving its global status, than risking direct confrontation with US and Europe.
North Korea getting into aggressive weapon grade nuclear production and also sprucing up its long range nuclear capable missiles, are a real threat not only to US / Japan and South Korea, but to the entire world. North Korea is capable of selling these nuclear loaded missiles to other fundamentalist rogue countries which has to stopped at all costs.