Everyone citing size of military as a reason why North Korea is a powerful nation:
Russia in the First World War. Russia had, by quite a long way, the largest army in the world. 15 million people fought in the Russian army from 1914-1917. And what happened? They were destroyed by the far smaller armies of Germany and Austro-Hungary.
Size counts for nothing. The North Korean army, like the Tsarist Russian army, is poorly trained, poorly equipped and poorly supplied.
EDIT: Also, in 2003 (last valid data), North Korean military expenditure was estimated at $5 billion. South Korean was $21 billion. South Korea has half as many active personnel in the army. So, spending per army member is eight times as high in South Korea as in the "DPR".