According to some high-ranking North Korean defectors, they actually built it themselves with no direct assistant from China or Russia -- which explains why they are so crappy. Their nuclear program is still young and poorly funded.
That's why I mentioned intelligence. You need proxy wars, coups, espionage, state-funded terrorism, etc etc in other countries to maintain your power. The US excels at that.
Look at south korea. Plenty of military, no brain.