The world knows of the decades of famine and starvation, the massive prison camps (you can even see these on Google Earth now), the terrible state of infrastructure, the lack of modern technology, the refugees trying to flee the country etc. The size of North Korean economy (24 million people) by GDP PPP (Purchasing Power Parity) is roughly similar to that of a little Baltic State of Latvia (2,2 million people). South Korean GDP is now 40 times greater than that of the North. South Koreans are on average 4,8 - 5 cm taller than their brethren in the North. Northerners simply don’t get enough to eat. A country that successfully tested a ballistic missile last December and conducted a third nuclear test in February recently cut the minimum height of its new army recruits to 142cm from the previous 145 cm. There are around one million men in the army which makes the North Korean army the 4th largest in the world. Militarization drains all resources from other spheres of the state and society, economic inefficiencies and mismanagement are inevitable as the command economy structure does not reward any initiative.
It appears logical that North Korea would have long perished as a state, were it not for the continuation of the Cold War - type great power struggles for influence. During the Cold War, the great powers found allies amongst poor and weak Middle Eastern, African, Asian and Latin American states. Those countries then struggled in endless conflicts, civil wars and real wars, often on behalf of their great power allies. The Soviets and the US never got into a direct military confrontation during four decades of global rivalry. Wars were conducted using the hands of Asians, Africans, Middle Easterners and Latin Americans while providing them with arms, training and economic support. The North Korean case is in many ways similar, except the actors have changed.