N Korea couldn't be achieving this without China's assistance. Is a coincidence that China has been instrumental for both N Korea and Iran, in their pursuit of nuclear weapons. The main target of both nations is the U.S.. Chinese generals are calling war with the U.S. "inevitable." China is expert at asymmetrical warfare. Letting someone else do it's dirty work would fit the bill.
Meanwhile, they lend us so much money that they hold sway over our economy. A Pentagon study fingered China as the culprit in the 2008 financial meltdown. They're attacking our satellites with lasers and damaging them. In the event of a war, we would be blinded if we lost our satellites. They are also constantly attacking us through cyber warfare.